JPH0786696A - Semiconductor optical element and semiconductor optical device using the same - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain a function as a semiconductor photodetector in a semiconductor optical device having a substrate made of a single crystal semiconductor and an active layer made of a single crystal semiconductor formed on the substrate. In such a case, the photodetection sensitivity of the semiconductor photodetector is made to hardly depend on the polarization mode of the signal light. [Structure] A well layer in which an active layer is formed by an epitaxial growth method using a single crystal semiconductor having a lattice constant equal to that of a single crystal semiconductor forming a substrate and a single crystal semiconductor forming a substrate A quantum well structure in which a barrier layer formed by using an epitaxial growth method in which a tensile strain is applied in a direction orthogonal to the growth direction of a single crystal semiconductor having a small lattice constant is sequentially laminated Have.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor optical device having a single crystal semiconductor substrate and an active layer formed on the single crystal semiconductor substrate, and a semiconductor optical device using the same.

[0001]

2. Description of the Related Art Conventionally, a semiconductor optical device M described below with reference to FIG. 8 has been proposed.

That is, a substrate 1 having, for example, n-type and made of, for example, single crystal InP, a single crystal semiconductor layer stack 2 formed on the substrate 1, and a single crystal semiconductor layer stack 2 of the substrate 1. It has an electrode layer 11 formed on the surface opposite to the side and an electrode layer 12 formed on the surface opposite to the substrate 1 side of the single crystal semiconductor layer stack 2.

In this case, the semiconductor layer stack 2 has an n-type clad layer 3 formed of, for example, single crystal InP and sequentially formed from the substrate 1 side by an epitaxial growth method. A guide layer 4 made of, for example, a single-crystal InGaAsP system having a lattice constant equal to that of single-crystal InP as a single-crystal semiconductor constituting the substrate 1.
An active layer 5 made of a single crystal semiconductor into which neither an n-type impurity nor a p-type impurity is intentionally introduced, and a single-crystal InP having a p-type and constituting the substrate 1 as a single-crystal semiconductor. Crystal InGaA having a lattice constant equal to
sP-based guide layer 6 and p-type and single crystal In
The clad layer 7 made of P and the cap layer 8 made of, for example, a single crystal InGaAsP system having a p-type and a lattice constant equal to that of single crystal InP as a single crystal semiconductor forming the substrate 1 are provided. The clad layer 3, the guide layer 4, the active layer 5, the guide layer 6, the clad layer 7 and the cap layer 8 have end faces 9a and 9b extending parallel to each other and facing each other in the stacking direction.

The active layer 5 forming the single crystal semiconductor layer stack 2 has a single crystal I having a lattice constant equal to that of the single crystal InP as the single crystal semiconductor forming the substrate 1.
A well layer 5a formed by an epitaxial growth method using a single crystal semiconductor made of nGaAs and a substrate 1
And a barrier layer 5b formed by an epitaxial growth method using a single-crystal InGaAsP-based single-crystal semiconductor having a lattice constant equal to that of the single-crystal InP as a single-crystal semiconductor constituting the above. It has a quantum well structure.

The above is the configuration of the conventionally proposed semiconductor optical device M.

According to the conventional semiconductor optical device M having such a structure, for example, as shown in FIG.
Is connected to the ground, the electrode layer 11 is connected to the negative power source E via the switching transistor Q which is turned on / off by the modulation signal S, and then to the negative power source E via the resistor R. Operational amplifier A having inputs a and b and one output c, with input b connected to ground and output c connected to input a through a feedback resistor Rf. Of the single crystal semiconductor layer laminated body 2 to the active layer 5 constituting the single crystal semiconductor layer laminated body 2 in a state where the switching transistor Q is turned off. If the signal light L is made incident from either one of the end surfaces 9a and 9b to be used by using an optical fiber (not shown), the detailed description is omitted, but the active layer 5 absorbs the signal light L. To increase the intensity of the signal light L For Flip photocurrent is generated, operator - optical voltage corresponding to the intensity of the signal light L to the output terminal c of the relational amplifier A is obtained.

Therefore, the signal light L can be detected by the optical voltage obtained at the output terminal c of the operation amplifier A, and thus the function as a semiconductor photodetector can be obtained.

Further, according to the conventional semiconductor optical device M shown in FIG. 8, the switching transistor Q is on / off controlled by a modulation signal in a state where the electrode layers 11 and 12 are connected as shown in FIG. Then, in the ON section, if a drive current is passed from the power source E side through the electrode layers 11 and 12 to the active layer 5 forming the semiconductor laminate 2, detailed description will be omitted, but in the active layer 5. The operation of generating light, propagating in the active layer 5 toward the end faces 9a and 9b, and then reflecting the end faces 9a and 9b is repeated. Therefore, the single crystal semiconductor layer stack 2
By properly selecting the distance between the end faces 9a and 9b of the laser, laser oscillation occurs, and the laser light L'based on the laser oscillation is emitted from either one of the end faces 9a and 9b. The light can be emitted to the outside, so that the function as a semiconductor laser can be obtained.

According to the conventional semiconductor optical device M shown in FIG. 8, the active layers 5 constituting the single crystal semiconductor layer stack 2 are formed by alternately stacking well layers 5a and barrier layers 5b. Since it has a quantum well structure, the function as a semiconductor photodetector and the function as a semiconductor laser,
The active layer 5 does not have such a quantum well structure and can be effectively obtained as compared with the case where it has a single layer structure.

[0001]

In the case of the conventional semiconductor optical device M shown in FIG. 8, the clad layer 3 forming the single crystal semiconductor layer stack 2 serves as the single crystal semiconductor forming the substrate 1. The guide layer 4 is formed by an epitaxial growth method using the same single crystal InP as the single crystal InP.
A single crystal I as a single crystal semiconductor constituting the substrate 1
The cladding layer 3 and the guide layer 4 have the same lattice arrangement as the substrate 1 because they are formed by the epitaxial growth method using a single crystal InGaAsP system having a lattice constant equal to nP.

Further, the active layer 5 constituting the single crystal semiconductor layer stack 2 has a quantum well structure in which well layers 5a and barrier layers 5b are alternately stacked, and the well layers 5a are formed. 9 is formed by an epitaxial growth method using a single crystal semiconductor 5a 'made of a single crystal InGaAs system having a lattice constant equal to that of single crystal InP as the single crystal semiconductor forming the substrate 1, as shown in FIG. Also,
The barrier layer 5b also has a single crystal I having a lattice constant equal to that of the single crystal InP as the single crystal semiconductor forming the substrate 1.
The well layer 5 is formed by the epitaxial growth method using a single crystal semiconductor of nGaAsP system.
The substrate 1 and the barrier layer 5b are not subjected to any tensile strain in the direction orthogonal to the growth direction when they are formed by the epitaxial growth method.
It has the same lattice arrangement as.

In the case of the conventional semiconductor optical device M shown in FIG. 8, both the well layer 5a and the barrier layer 5b forming the active layer 5 of the single crystal semiconductor layer stack 2 are, as described above, Since it has the same lattice arrangement as the substrate 1 in the state where no tensile strain is applied in the direction orthogonal to the growth direction when it is formed by the epitaxial growth method,
The active layer 5 has the energy band structure described below.

That is, as shown in FIG. 10, the band edge of the conduction band and the band edge of the valence band are both in the well layer 5a forming the active layer 5 and in the barrier layer 5b. One of the well layers 5a has electron quantum levels Ec on the side opposite to the band edge side of the valence band as viewed from the band edge of the conduction band in the well layer 5a.
Existing over the entire area in the thickness direction of the barrier layer 5
It does not exist in b except that it slightly exudes from the well layer 5a side, and the quantum level Ehh of the heavy hole is
The well layer 5a exists over the entire region in the thickness direction of the well layer 5a on the side opposite to the band edge side of the conduction band when viewed from the band edge of the valence band, but inside the barrier layer 5b. It does not exist except that it slightly exudes from the well layer 5a side. Furthermore, the quantum level Elh of the light hole is
In a, on the side opposite to the band edge side of the valence band as viewed from the quantum level Ehh, the well layer 5 is formed in the same manner as the quantum level Ehh.
It exists over the entire area of a in the thickness direction, but does not exist in the barrier layer 5b except that it slightly exudes from the well layer 5a side.

For this reason, that is, since the active layer 5 has the above-mentioned energy band structure, the signal light L is a single crystal semiconductor layer laminated body when the function as the above-mentioned semiconductor photodetector is obtained. When the signal light L is absorbed by the active layer 5 constituting the second light source 2,
In the E mode, electrons are generated in the well layer 5a,
The signal light L is generated by the transition mainly between the electron quantum level Ec and the heavy-hole quantum level Ehh.
In the case of the M mode, electrons are mainly generated in the well layer 5a by the transition between the quantum level Ec and the quantum level Elh of the light hole.

In this case, the quantum level Elh of the light hole existing in the well layer 5a is, as described above, evaluated from the quantum level Ehh of the heavy hole existing in the well layer 5a. Since the electron exists on the side opposite to the band edge side of the electron band, when the signal light L is in TM mode, the electrons move from the electron quantum level Ec to the light hole quantum level Elh.
The probability of the transition to (1) is sufficiently smaller than the probability that the electron transits from the electron quantum level Ec to the heavy hole quantum level Ehh when the signal light L is in the TE mode. Therefore, when the signal light L is in TM mode, the well layer 5
The absorption coefficient of the signal light L that is absorbed in a is T
In the case of the E mode, it is sufficiently smaller than the absorption coefficient absorbed in the well layer 5a.

From the above, according to the conventional semiconductor optical device shown in FIG. 8, when it has a function as a semiconductor photodetector, the photodetection sensitivity of the semiconductor photodetector is that of the incident signal light L. It has a drawback that it largely depends on whether it is TE mode or TM mode.

Therefore, the present invention does not have the drawbacks mentioned above,
A novel semiconductor optical device and a semiconductor optical device using the same are proposed.

[0001]

A semiconductor optical device according to the present invention includes a substrate made of a single crystal semiconductor and a single substrate formed on the substrate, as in the case of the conventional semiconductor optical device described in FIG. And an active layer made of a crystalline semiconductor.

However, in the semiconductor optical device according to the present invention, in the semiconductor optical device having such a structure, the active layer uses a single crystal semiconductor having a lattice constant equal to that of the single crystal semiconductor forming the substrate. And a well layer formed by an epitaxial growth method and a single crystal semiconductor having a lattice constant smaller than that of the single crystal semiconductor forming the substrate are used, the tensile strain is generated in the direction orthogonal to the growth direction by the epitaxial growth method. It has a quantum well structure in which barrier layers formed in a given state are sequentially laminated alternately.

Further, a semiconductor optical device according to the present invention has a plurality of semiconductor optical elements formed by using a substrate made of a single crystal semiconductor, and each of the plurality of semiconductor optical elements is on the substrate. A single crystal semiconductor having an active layer formed of a single crystal semiconductor, and each active layer of the plurality of semiconductor optical elements has a lattice constant equal to that of the single crystal semiconductor forming the substrate. A well layer formed by an epitaxial growth method using a single crystal semiconductor having a lattice constant smaller than that of the single crystal semiconductor forming the substrate is used, and a tensile strain is applied in a direction orthogonal to the growth direction by the epitaxial growth method. Has a quantum well structure in which barrier layers formed in a given state are sequentially stacked alternately.

[0001]

According to the semiconductor optical device of the present invention, when the signal light is incident on the active layer, the signal light is incident on the active layer as in the case of the conventional semiconductor optical device described above with reference to FIG. Is absorbed, a photocurrent corresponding to the intensity of the signal light is generated. Therefore, the signal light can be detected as in the case of the conventional semiconductor optical device described above with reference to FIG.
Similar to the case of the conventional semiconductor optical device described above with reference to FIG. 8, a function as a semiconductor photodetector can be obtained.

According to the semiconductor optical device of the present invention, when a drive current is applied to the active layer, the active layer of FIG.
As in the case of the conventional semiconductor optical device described above in 1., laser oscillation occurs due to the generation of light, as in the case of the conventional semiconductor optical device described in FIG. Originally, the laser light can be emitted to the outside as in the case of the conventional semiconductor optical device described above with reference to FIG. 8. Therefore, as in the case of the conventional semiconductor optical device described above with reference to FIG. -You can get the function.

According to the semiconductor optical device of the present invention, the active layer has a quantum well structure in which well layers and barrier layers are alternately laminated in the same manner as in the conventional semiconductor optical device described above with reference to FIG. Since it has a well structure, the active layer has such a function as a semiconductor photodetector and a semiconductor laser as in the case of the conventional semiconductor optical device described above with reference to FIG. It can be effectively obtained as compared with the case where it has no structure and has a single-layer structure.

However, in the case of the semiconductor optical device according to the present invention, the active layer forming the single crystal semiconductor layer stack has the energy band structure described below.

That is, unlike the case of the conventional semiconductor optical device described above with reference to FIG. 8, since the barrier layer forming the active layer is in the state of being subjected to tensile strain, the band edge of the conduction band and As in the case of the conventional semiconductor optical device described above with reference to FIG. 8, each of the valence band band edges has one in the well layer that constitutes the active layer, and the conduction band edge has the barrier layer. In the barrier layer, the band edge of the valence band has two, the band edge by the light hole and the band edge by the heavy hole below it. There is.

Therefore, as in the case of the conventional semiconductor optical device described above with reference to FIG. 8, the quantum level of electrons is different from the band edge side of the valence band in the well layer when viewed from the band edge of the conduction band. It exists over the entire area in the thickness direction of the well layer on the opposite side, but does not exist in the barrier layer except for slightly exuding from the well layer side. As in the case of the conventional semiconductor optical device described above with reference to FIG. 8, in the well layer, the thickness of the well layer is on the side opposite to the band edge side of the conduction band when viewed from the band edge of the valence band. Although it exists over the entire area in the depth direction, but does not exist in the barrier layer except for slightly exuding from the well layer side, the quantum level of the light hole is in the well layer, The barrier layer is on the side opposite to the band edge side of the valence band as seen from the heavy hole quantum level. It is present over the entire area in the thickness direction, but the well layers does not exist except as seeping slightly from the barrier layer side.

For this reason, that is, since the active layer has the above-mentioned energy band structure, the signal light constitutes the single crystal semiconductor layer laminated body when the function as the semiconductor photodetector is obtained. When the signal light is absorbed in the active layer, the electrons are absorbed in the well layer when the signal light is in TM mode, as in the case of the conventional semiconductor optical device described above with reference to FIG. In the case where the signal light is TM mode, the conventional semiconductor light described above with reference to FIG. 8 is generated by the transition between the electron quantum level and the heavy hole quantum level. Similar to the case of the device, even if electrons are generated in the well layer by a transition between the quantum level of the electron and the portion of the quantum level of the light hole that exudes in the well layer, In this case, the well layer exudes from the barrier layer side. As described above, the quantum level of ithole exists on the opposite side of the band edge side of the valence band from the viewpoint of the quantum level of the heavy hole existing in the well layer. Even if the quantum level of the light hole seeping out from the barrier layer side in the well layer exists only in the state localized in the well layer, the signal light is in TM mode. In this case, the probability that an electron transits from the quantum level of the electron to the quantum level of the light hole is high in the case of the conventional semiconductor optical device described above with reference to FIG. 8. Therefore, the signal light is in TM mode. In the case where the electron transits from the electron quantum level to the light hole quantum level, and when the signal light is in TE mode, the electron moves from the electron quantum level to the heavy hole quantum level. There is almost no difference with the probability of transitioning to the rank, or the difference, if any. Small enough. Therefore, when the signal light is in the TM mode, the absorption coefficient is absorbed in the well layer, and when the signal light is in the TE mode, the absorption coefficient is absorbed in the well layer. There is little difference, or if there is a difference, the difference is small enough.

From the above, in the case of the semiconductor optical device according to the present invention, when it has a function as a semiconductor photodetector,
The photodetection sensitivity of the semiconductor photodetector hardly depends on whether the incident signal light is in TE mode or TM mode.

According to the semiconductor optical device of the present invention, a plurality of semiconductor optical devices according to the first invention of the present application are provided.
Since it has a structure in which the substrate is common,
For each semiconductor optical device, the same operational effects as those of the semiconductor optical device according to the first invention of the present application can be obtained.

[0001]

Embodiment 1 Next, an embodiment of a semiconductor optical device according to the present invention will be described with reference to FIG.

In FIG. 1, parts corresponding to those in FIG. 8 are designated by the same reference numerals.

A semiconductor optical device according to the present invention shown in FIG.
Similar to the case of the conventional semiconductor optical device described above with reference to FIG. 8, that is, a substrate 1 having, for example, n-type and made of, for example, single crystal InP, and a single crystal semiconductor layer stack formed on the substrate 1. 2, an electrode layer 11 formed on the surface of the substrate 1 opposite to the single crystal semiconductor layer laminate 2 side, and an electrode layer 11 formed on the surface of the single crystal semiconductor layer laminate 2 opposite to the substrate 1 side. And the formed electrode layer 12.

In this case, the semiconductor layer laminate 2 has an n-type, which is formed by sequentially laminating from the substrate 1 side by the epitaxial growth method, as in the case of the conventional semiconductor optical device described above with reference to FIG. And a cladding layer 3 made of, for example, single crystal InP, and a guide layer 4 made of, for example, single crystal InGaAsP having an n-type and a lattice constant equal to that of single crystal InP as a single crystal semiconductor constituting the substrate 1.
An active layer 5 made of a single crystal semiconductor into which neither an n-type impurity nor a p-type impurity is intentionally introduced, and a single-crystal InP having a p-type and constituting the substrate 1 as a single-crystal semiconductor. Crystal InGaA having a lattice constant equal to
sP-based guide layer 6 and p-type and single crystal In
The clad layer 7 made of P and the cap layer 8 made of, for example, a single crystal InGaAsP system having a p-type and a lattice constant equal to that of single crystal InP as a single crystal semiconductor forming the substrate 1 are provided. The clad layer 3, the guide layer 4, the active layer 5, the guide layer 6, the clad layer 7 and the cap layer 8 have end faces 9a and 9b extending parallel to each other and facing each other in the stacking direction.

However, in the case of the semiconductor optical device according to the present invention shown in FIG. 1, the active layer 5 forming the single crystal semiconductor layer stack 2 is a single crystal InP as a single crystal semiconductor forming the substrate 1. Crystal I having a lattice constant equal to
A well layer 15a formed by an epitaxial growth method using a single crystal semiconductor made of nGaAs and a single crystal InGaAsP system having a smaller lattice constant than single crystal InP as the single crystal semiconductor forming the substrate 1 Has a quantum well structure in which barrier layers 15b formed by an epitaxial growth method using the following single crystal semiconductor are sequentially laminated alternately.

The above is the configuration of the embodiment of the semiconductor optical device according to the present invention.

According to the semiconductor optical device M of the present invention having such a configuration, as described in the conventional semiconductor optical device M, for example, as shown in FIG. 11, the electrode layer 12 is connected to the ground, and the electrode The layer 11 is connected to a negative power source E via a switching transistor Q which is turned on / off by a modulation signal S and then via a resistor R, and two input terminals a and b and 1 having opposite polarities to each other. Connected to the input terminal b of the operational amplifier A having two output terminals c, the input terminal b is connected to the ground, and the output terminal c is connected to the input terminal a through the feedback resistor Rf. , And then
With the switching transistor Q turned off, the active layer 5 constituting the single crystal semiconductor layer stack 2 is formed.
In addition, an optical fiber (not shown) is provided from either one of the opposite end faces 9a and 9b of the single crystal semiconductor layer stack 2.
If the signal light L is incident on the active layer 5, a detailed description will be omitted, but since the active layer 5 absorbs the signal light L, a photocurrent corresponding to the intensity of the signal light L is generated.
An optical voltage corresponding to the intensity of the signal light L is obtained at the output terminal c of the optional amplifier A.

Therefore, the signal light L can be detected by the optical voltage obtained at the output terminal c of the operation amplifier A, as in the case of the conventional semiconductor optical device described above with reference to FIG. The function as a semiconductor photodetector can be obtained.

Further, while the electrode layers 11 and 12 are connected as shown in FIG. 9, the switching transistor Q is controlled to be turned on / off by a modulation signal, and in the on section, from the power source E side to the electrode layer. If a drive current is passed through the active layer 5 forming the semiconductor laminate 2 through 11 and 12, light will be generated in the active layer 5 and the light will be generated in the active layer 5 although detailed description is omitted. Is propagated toward the end faces 9a and 9b, and then reflected by the end faces 9a and 9b. Therefore, by appropriately selecting the distance between the end faces 9a and 9b of the single crystal semiconductor layer stack 2 in advance, laser oscillation occurs and the laser light L'based on the laser oscillation is generated. The light can be emitted to the outside from either one of the end faces 9a and 9b, so that the function as a semiconductor laser can be obtained.

Furthermore, since the active layer 5 constituting the single crystal semiconductor layer stack 2 has a quantum well structure in which well layers 15a and barrier layers 15b are alternately stacked,
The function as a semiconductor photodetector and the function as a semiconductor laser described above are effectively obtained compared to the case where the active layer 5 does not have such a quantum well structure and has a single layer structure. be able to.

In the case of the semiconductor optical device M, the same single crystal InP as the single crystal InP as the single crystal semiconductor forming the substrate 1 is used as the cladding layer 3 forming the single crystal semiconductor layer stack 2. Is formed by an epitaxial growth method, and the guide layer 4 is formed by an epitaxial growth method using a single crystal InGaAsP system having a lattice constant equal to that of single crystal InP as the single crystal semiconductor forming the substrate 1. The clad layer 3 and the guide layer 4 have the same lattice arrangement as the substrate 1.

However, the active layer 5 constituting the single crystal semiconductor layer stack 2 is composed of the well layer 15a and the barrier layer 15.
b has a quantum well structure in which layers b and are sequentially stacked alternately,
Then, as shown in FIG. 2, the well layer 15a is epitaxially grown using a single crystal InGaAs-based single crystal semiconductor 15a 'having a lattice constant equal to that of the single crystal InP as the single crystal semiconductor forming the substrate 1. The barrier layer 15b is formed by the epitaxial growth method using a single crystal semiconductor made of a single crystal InGaAsP system having a smaller lattice constant than the single crystal InP as the single crystal semiconductor forming the substrate 1. And has the same lattice arrangement as that of the substrate 1 in a state where no tensile strain is applied in the direction orthogonal to the growth direction when the barrier layer 15b is formed by the epitaxial growth method.

For this reason, the active layer 5 has the energy band structure as shown in FIG.

For this reason, that is, since the active layer 5 has the above-mentioned energy band structure, light absorption is caused by the transition described in the section of the action and effect.

From the above, according to the semiconductor optical device of the present invention, when the function as a semiconductor photodetector is obtained, the photodetection sensitivity of the semiconductor photodetector is such that the incident signal light L is TE -It does not largely depend on whether it is the mode or the TM mode.

That is, according to the semiconductor optical device of the present invention, when the signal light is incident on the active layer, the signal light is incident on the active layer as in the case of the conventional semiconductor optical device described in FIG. Is absorbed, a photocurrent corresponding to the intensity of the signal light is generated. Therefore, the signal light can be detected as in the case of the conventional semiconductor optical device described above with reference to FIG. As in the case of the conventional semiconductor optical device described above, the function as a semiconductor photodetector can be obtained.

According to the semiconductor optical device of the present invention, when a drive current is applied to the active layer, the active layer of FIG.
As in the case of the conventional semiconductor optical device described above in 1., laser oscillation occurs due to the generation of light, as in the case of the conventional semiconductor optical device described in FIG. Originally, the laser light can be emitted to the outside as in the case of the conventional semiconductor optical device described above with reference to FIG. 8. Therefore, as in the case of the conventional semiconductor optical device described above with reference to FIG. -You can get the function.

According to the semiconductor optical device of the present invention, the active layer has a quantum well structure in which well layers and barrier layers are alternately laminated in the same manner as in the conventional semiconductor optical device described above with reference to FIG. Since it has a well structure, the active layer has such a function as a semiconductor photodetector and a semiconductor laser as in the case of the conventional semiconductor optical device described above with reference to FIG. It can be effectively obtained as compared with the case where it has no structure and has a single-layer structure.

However, in the case of the semiconductor optical device according to the present invention, the active layer forming the single crystal semiconductor layer stack has the energy band structure described below.

That is, unlike the case of the conventional semiconductor optical device described above with reference to FIG. 8, since the barrier layer forming the active layer is in the state of being subjected to tensile strain, the band edge of the conduction band and As in the case of the conventional semiconductor optical device described above with reference to FIG. 8, each of the valence band band edges has one in the well layer that constitutes the active layer, and the conduction band edge has the barrier layer. In the barrier layer, the band edge of the valence band has two, the band edge by the light hole and the band edge by the heavy hole below it. There is. Therefore, the quantum level of the electron is
As in the case of the conventional semiconductor optical device described above with reference to FIG. 8, the well layer extends over the entire region in the thickness direction of the well layer on the side opposite to the band edge side of the valence band as seen from the band edge of the conduction band. However, it does not exist in the barrier layer except for slightly exuding from the well layer side.
As in the case of the conventional semiconductor optical device described above with reference to FIG. 8, in the well layer, the quantum level of the quantum well is on the side opposite to the band edge side of the conduction band as viewed from the band edge of the valence band. Although it exists over the entire area in the thickness direction of the layer, it does not exist in the barrier layer except for slightly exuding from the well layer side, but the quantum level of the light hole is in the well layer. Exists over the entire region in the thickness direction of the barrier layer on the side opposite to the band edge side of the valence band as viewed from the heavy hole quantum level, but the barrier layer is present in the well layer. It does not exist except that it slightly exudes from the layer side.

For this reason, that is, since the active layer has the above-mentioned energy band structure, the signal light constitutes the single crystal semiconductor layer laminated body when the function as the semiconductor photodetector is obtained. When the signal light is absorbed in the active layer, the electrons are absorbed in the well layer when the signal light is in TM mode, as in the case of the conventional semiconductor optical device described above with reference to FIG. In the case where the signal light is TM mode, the conventional semiconductor light described above with reference to FIG. 8 is generated by the transition between the electron quantum level and the heavy hole quantum level. Similar to the case of the device, even if electrons are generated in the well layer by a transition between the quantum level of the electron and the portion of the quantum level of the light hole that exudes in the well layer, In this case, the well layer exudes from the barrier layer side. As described above, the quantum level of ithole exists on the opposite side of the band edge side of the valence band from the viewpoint of the quantum level of the heavy hole existing in the well layer. Even if the quantum level of the light hole seeping out from the barrier layer side in the well layer exists only in the state localized in the well layer, the signal light is in TM mode. In this case, the probability that an electron transits from the quantum level of the electron to the quantum level of the light hole is high in the case of the conventional semiconductor optical device described above with reference to FIG. 8. Therefore, the signal light is in TM mode. In the case where the electron transits from the electron quantum level to the light hole quantum level, and when the signal light is in TE mode, the electron moves from the electron quantum level to the heavy hole quantum level. There is almost no difference with the probability of transitioning to the rank, or the difference, if any. Small enough. Therefore, when the signal light is in the TM mode, the absorption coefficient is absorbed in the well layer, and when the signal light is in the TE mode, the absorption coefficient is absorbed in the well layer. There is little difference, or if there is a difference, the difference is small enough.

From the above, in the case of the semiconductor optical device according to the present invention, when it has a function as a semiconductor photodetector,
The photodetection sensitivity of the semiconductor photodetector hardly depends on whether the incident signal light is in TE mode or TM mode.

This means that the same signal light L is used in the case of the semiconductor optical device according to the present invention shown in FIG. 1 and the case of the conventional semiconductor optical device described in FIG. 8, and the light detection sensitivity is 10 log. When the polarization dependence defined as (I min / I max) was measured by changing the wavelength, the results shown in FIG. 4 were obtained, and the photodetection sensitivity of the semiconductor optical device according to the present invention shown in FIG. 1 was measured. However, it will be clear from the results shown in FIG.

According to the semiconductor optical device according to the present invention shown in FIG. 1, when the function as the semiconductor laser described above is obtained, the optical output by the laser light with respect to the driving current is measured. As shown in FIG. 6, the result that the deviation of the wavelength of 1550 nm occurs at the threshold value of the driving current of 20 nA and the optical output of 5 mW is obtained when the driving current is 30 mA.

[0001]

[Embodiment 2] Next, an embodiment of a semiconductor optical device according to the present invention using the semiconductor optical element according to the present invention will be described with reference to FIG.

A semiconductor optical device according to the present invention shown in FIG.
In the semiconductor optical device M according to the present invention described above with reference to FIG. 1, a plurality of grooves are formed side by side from the electrode layer 12 side across the single crystal semiconductor layer stack 2 to a depth reaching the substrate 1. Then, a plurality of n semiconductor optical devices M1, M2 ... Mn are formed with the substrate 1 in common between the adjacent grooves.

The above is the configuration of the embodiment of the semiconductor optical device according to the present invention.

According to the semiconductor optical device of the present invention having such a structure, a plurality of n semiconductor optical elements M1 to Mn are provided.
Since each of them has the same structure as the outside according to the present invention shown in FIG. 1, the same operation as in the case of the semiconductor optical device according to the present invention shown in FIG. It is clear that the effect can be obtained.

In the above description, each of the semiconductor optical device and the semiconductor optical device according to the present invention is 1
Only one embodiment is shown, and various modifications and changes can be made without departing from the spirit of the present invention.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an embodiment of a semiconductor optical device according to the present invention.

FIG. 2 is a view showing an active layer of the semiconductor optical device according to the present invention shown in FIG.

FIG. 3 is a diagram showing the mechanism of signal light absorption in the active layer of the semiconductor optical device according to the present invention shown in FIG. 1, together with the energy band structure of the active layer.

FIG. 4 is a diagram showing the polarization dependence of an optical signal with respect to the wavelength of the optical signal when the function as a photodetector is obtained by the semiconductor optical device according to the present invention shown in FIG. It is a figure which shows in comparison with the polarization dependence of the optical signal with respect to the wavelength of an optical signal when the function as a container is acquired.

5 is a diagram showing photodetection sensitivity with respect to wavelength when a function as a photodetector is obtained by the semiconductor optical device according to the present invention shown in FIG.

FIG. 6 is a diagram showing a relationship between a drive current and an optical output when the semiconductor optical device according to the present invention shown in FIG. 1 obtains a function as a semiconductor laser.

FIG. 7 is a schematic plan view showing an embodiment of a semiconductor optical device according to the present invention.

FIG. 8 is a schematic cross-sectional view showing a conventional semiconductor optical device.

9 is a diagram showing an active layer of the conventional semiconductor optical device shown in FIG.

FIG. 10 is a diagram for explaining the conventional semiconductor optical device shown in FIG.

11 is a diagram showing a circuit for obtaining a function as a photodetector and a function as a semiconductor laser by the semiconductor optical device according to the present invention shown in FIG. 1 and the conventional semiconductor optical device shown in FIG. .

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 substrate 2 single crystal semiconductor layer laminated body 3 cladding layer 4 guide layer 5 active layer 5a well layer 5b barrier layer 6 guide layer 7 cladding layer 8 cap layer 9a, 9b end face 11, 12 electrode layer 15a well layer 15b barrier layer A amplifier M semiconductor optical device Q switching transistor

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[Procedure amendment]

[Submission date] October 15, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Title: Semiconductor optical device and semiconductor optical device using the same

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor optical device having a single crystal semiconductor substrate and an active layer formed on the single crystal semiconductor substrate, and a semiconductor optical device using the same.

[0002]

2. Description of the Related Art Conventionally, a semiconductor optical device M described below with reference to FIG. 8 has been proposed.

That is, a substrate 1 having, for example, n-type and made of, for example, single crystal InP, a single crystal semiconductor layer stack 2 formed on the substrate 1, and a single crystal semiconductor layer stack 2 of the substrate 1. It has an electrode layer 11 formed on the surface opposite to the side and an electrode layer 12 formed on the surface opposite to the substrate 1 side of the single crystal semiconductor layer stack 2.

In this case, the semiconductor layer laminated body 2 has an n-type clad layer 3 formed of, for example, single crystal InP and formed by sequentially laminating from the substrate 1 side by an epitaxial growth method, and an n-type. A guide layer 4 made of, for example, a single-crystal InGaAsP system having a lattice constant equal to that of single-crystal InP as a single-crystal semiconductor constituting the substrate 1.
An active layer 5 made of a single crystal semiconductor into which neither an n-type impurity nor a p-type impurity is intentionally introduced, and a single-crystal InP having a p-type and constituting the substrate 1 as a single-crystal semiconductor. Crystal InGaA having a lattice constant equal to
sP-based guide layer 6 and p-type and single crystal In
The clad layer 7 made of P and the cap layer 8 made of, for example, a single crystal InGaAsP system having a p-type and a lattice constant equal to that of single crystal InP as a single crystal semiconductor forming the substrate 1 are provided. The clad layer 3, the guide layer 4, the active layer 5, the guide layer 6, the clad layer 7 and the cap layer 8 have end faces 9a and 9b extending parallel to each other and facing each other in the stacking direction.

The active layer 5 forming the single crystal semiconductor layer stack 2 has a single crystal I having a lattice constant equal to that of the single crystal InP as the single crystal semiconductor forming the substrate 1.
A well layer 5a formed by an epitaxial growth method using a single crystal semiconductor made of nGaAs and a substrate 1
And a barrier layer 5b formed by an epitaxial growth method using a single-crystal InGaAsP-based single-crystal semiconductor having a lattice constant equal to that of the single-crystal InP as a single-crystal semiconductor constituting the above. It has a quantum well structure.

The above is the configuration of the conventionally proposed semiconductor optical device M.

According to the conventional semiconductor optical device M having such a structure, for example, as shown in FIG.
Is connected to the ground, the electrode layer 11 is connected to the negative power source E via the switching transistor Q which is turned on / off by the modulation signal S, and then to the negative power source E via the resistor R. Operational amplifier having inputs a and b and one output c, the input b is connected to ground, and the output c is connected to the input a through a feedback resistor R _f . The single crystal semiconductor layer stack 2 is connected to the active layer 5 that constitutes the single crystal semiconductor layer stack 2 in a state where the single crystal semiconductor layer stack 2 is connected to the input terminal b of A and the switching transistor Q is turned off. If the signal light L is made incident from either one of the facing end faces 9a and 9b using an optical fiber (not shown), the detailed description will be omitted, but the signal light L will enter the active layer 5. By being absorbed, the intensity of the signal light L is increased. For Flip photocurrent is generated, operator - optical voltage corresponding to the intensity of the signal light L to the output terminal c of the relational amplifier A is obtained.

Therefore, the signal light L can be detected by the optical voltage obtained at the output terminal c of the operation amplifier A, and thus the function as the semiconductor photodetector can be obtained.

Further, according to the conventional semiconductor optical device M shown in FIG. 8, the switching transistor Q is on / off controlled by a modulation signal in a state where the electrode layers 11 and 12 are connected as shown in FIG. Then, in the ON section, if a drive current is passed from the power source E side through the electrode layers 11 and 12 to the active layer 5 forming the semiconductor laminate 2, detailed description will be omitted, but in the active layer 5. The operation of generating light, propagating in the active layer 5 toward the end faces 9a and 9b, and then reflecting the end faces 9a and 9b is repeated. Therefore, the single crystal semiconductor layer stack 2
By properly selecting the distance between the end faces 9a and 9b of the laser, laser oscillation occurs, and the laser light L'based on the laser oscillation is emitted from either one of the end faces 9a and 9b. The light can be emitted to the outside, so that the function as a semiconductor laser can be obtained.

According to the conventional semiconductor optical device M shown in FIG. 8, the active layers 5 constituting the single crystal semiconductor layer stack 2 are formed by alternately stacking well layers 5a and barrier layers 5b. Since it has a quantum well structure, the function as a semiconductor photodetector and the function as a semiconductor laser,
The active layer 5 does not have such a quantum well structure and can be effectively obtained as compared with the case where it has a single layer structure.

[0011]

In the case of the conventional semiconductor optical device M shown in FIG. 8, the clad layer 3 forming the single crystal semiconductor layer stack 2 serves as the single crystal semiconductor forming the substrate 1. The guide layer 4 is formed by an epitaxial growth method using the same single crystal InP as the single crystal InP.
A single crystal I as a single crystal semiconductor constituting the substrate 1
The cladding layer 3 and the guide layer 4 have the same lattice arrangement as the substrate 1 because they are formed by the epitaxial growth method using a single crystal InGaAsP system having a lattice constant equal to nP.

Further, the active layer 5 constituting the single crystal semiconductor layer stack 2 has a quantum well structure in which well layers 5a and barrier layers 5b are alternately stacked, and the well layers 5a are formed. 9 is formed by an epitaxial growth method using a single crystal semiconductor 5a 'made of a single crystal InGaAs system having a lattice constant equal to that of single crystal InP as the single crystal semiconductor forming the substrate 1, as shown in FIG. Also,
The barrier layer 5b also has a single crystal I having a lattice constant equal to that of the single crystal InP as the single crystal semiconductor forming the substrate 1.
Since the single crystal semiconductor 5b 'made of nGaAsP is formed by the epitaxial growth method, both the well layer 5a and the barrier layer 5b are perpendicular to the growth direction when they are formed by the epitaxial growth method. With no tensile strain applied to the
It has the same lattice arrangement as the substrate 1.

Further, in the case of the conventional semiconductor optical device M shown in FIG. 8, both the well layer 5a and the barrier layer 5b forming the active layer 5 of the single crystal semiconductor layer stack 2 are as described above. Since it has the same lattice arrangement as the substrate 1 in the state where no tensile strain is applied in the direction orthogonal to the growth direction when it is formed by the epitaxial growth method,
The active layer 5 has the energy band structure described below.

That is, as shown in FIG. 11, the band edge of the conduction band and the band edge of the valence band are both in the well layer 5a forming the active layer 5 and in the barrier layer 5b. Each of them has a quantum level E _c of electrons in the well layer 5a on the side opposite to the band edge side of the valence band when viewed from the band edge of the conduction band in the well layer 5a.
Existing over the entire area in the thickness direction of the barrier layer 5
It does not exist in the region b except that it slightly exudes from the well layer 5a side, and the quantum level E _hh of the _heavy hole is
The well layer 5a exists over the entire region in the thickness direction of the well layer 5a on the side opposite to the band edge side of the conduction band when viewed from the band edge of the valence band, but inside the barrier layer 5b. It does not exist except that it slightly exudes from the well layer 5a side. Further, the quantum level E _lh of the light hole is
In a, on the side opposite to the band edge side of the valence band as _viewed from the quantum level E _hh , similarly to the quantum level E _hh , the well layer 5
It exists over the entire area of a in the thickness direction, but does not exist in the barrier layer 5b except that it slightly exudes from the well layer 5a side.

For this reason, that is, since the active layer 5 has the above-mentioned energy band structure, the signal light L has the single crystal semiconductor layer laminated body when the above-mentioned function as the semiconductor photodetector is obtained. When the signal light L is absorbed by the active layer 5 constituting the second light source 2,
In the E mode, electrons are generated in the well layer 5a,
The signal light L is generated by the transition mainly between the electron quantum level E _c and the heavy-hole quantum level E _hh ,
In the M mode, electrons are mainly generated in the well layer 5a by the transition between the quantum level E _c and the quantum level E _lh of the light hole.

In this case, the quantum level E _lh of the light hole existing in the well layer 5a is calculated from the quantum level E _{hh of} the heavy hole existing in the well layer 5a as described above. Since the electron exists on the side opposite to the band edge side of the valence band, when the signal light L is in TM mode, the electron moves from the electron quantum level E _c to the light hole quantum level E _{c. lh}
The probability of transition to the quantum level E _hh of the electron from the electron quantum level E _c to the heavy hole quantum level E _hh is sufficiently small when the signal light L is in the TE _mode . Therefore,
When the signal light L is in TM mode, the absorption coefficient thereof is absorbed in the well layer 5a, and when the signal light L is in TE mode, it is absorbed in the well layer 5a. Then small enough.

From the above, according to the conventional semiconductor optical device shown in FIG. 8, when the function as a semiconductor photodetector is obtained, the photodetection sensitivity of the semiconductor photodetector is such that the incident signal light is incident. Whether L is in TE mode or TM mode, that is, greatly depends on the polarization mode of the signal light L,
It had a drawback.

Therefore, the present invention does not have the above-mentioned drawbacks.
A novel semiconductor optical device and a semiconductor optical device using the same are proposed.

[0019]

A semiconductor optical device according to the present invention includes a substrate made of a single crystal semiconductor and a single substrate formed on the substrate, as in the case of the conventional semiconductor optical device described in FIG. And an active layer made of a crystalline semiconductor.

However, in the semiconductor optical device according to the present invention, in the semiconductor optical device having such a structure, the active layer uses a single crystal semiconductor having a lattice constant equal to that of the single crystal semiconductor forming the substrate. And a well layer formed by an epitaxial growth method and a single crystal semiconductor having a lattice constant smaller than that of the single crystal semiconductor forming the substrate are used, the tensile strain is generated in the direction orthogonal to the growth direction by the epitaxial growth method. It has a quantum well structure in which barrier layers formed in a given state are sequentially laminated alternately.

Further, the semiconductor optical device according to the present invention has a plurality of semiconductor optical elements formed by using a substrate made of a single crystal semiconductor, and each of the plurality of semiconductor optical elements is on the substrate. A single crystal semiconductor having an active layer formed of a single crystal semiconductor, and each active layer of the plurality of semiconductor optical elements has a lattice constant equal to that of the single crystal semiconductor forming the substrate. A well layer formed by an epitaxial growth method using a single crystal semiconductor having a lattice constant smaller than that of the single crystal semiconductor forming the substrate is used, and a tensile strain is applied in a direction orthogonal to the growth direction by the epitaxial growth method. Has a quantum well structure in which barrier layers formed in a given state are sequentially stacked alternately.

[0022]

According to the semiconductor optical device of the present invention, when the signal light is incident on the active layer, the signal light is incident on the active layer as in the case of the conventional semiconductor optical device described above with reference to FIG. Is absorbed, a photocurrent corresponding to the intensity of the signal light is generated. Therefore, the signal light can be detected as in the case of the conventional semiconductor optical device described above with reference to FIG.
Similar to the case of the conventional semiconductor optical device described above with reference to FIG. 8, a function as a semiconductor photodetector can be obtained.

Further, according to the semiconductor optical device of the present invention, when a drive current is applied to the active layer, the active layer shown in FIG.
As in the case of the conventional semiconductor optical device described above in 1., laser oscillation occurs due to the generation of light, as in the case of the conventional semiconductor optical device described in FIG. Originally, the laser light can be emitted to the outside as in the case of the conventional semiconductor optical device described above with reference to FIG. 8. Therefore, as in the case of the conventional semiconductor optical device described above with reference to FIG. -You can get the function.

According to the semiconductor optical device of the present invention, the active layer has a quantum well structure in which well layers and barrier layers are alternately laminated in the same manner as in the conventional semiconductor optical device described above with reference to FIG. Since it has a well structure, the active layer has such a function as a semiconductor photodetector and a semiconductor laser as in the case of the conventional semiconductor optical device described above with reference to FIG. It can be effectively obtained as compared with the case where it has no structure and has a single-layer structure.

However, in the case of the semiconductor optical device according to the present invention, the active layer forming the single crystal semiconductor layer stack has the energy band structure described below.

That is, unlike the case of the conventional semiconductor optical device described above with reference to FIG. 8, since the barrier layer forming the active layer is in the state of being subjected to tensile strain, the band edge of the conduction band and the As in the case of the conventional semiconductor optical device described above with reference to FIG. 8, each of the valence band band edges has one in the well layer that constitutes the active layer, and the conduction band edge has the barrier layer. In the barrier layer, the band edge of the valence band has two, the band edge by the light hole and the band edge by the heavy hole below it. There is.

Therefore, as in the case of the conventional semiconductor optical device described above with reference to FIG. 8, the quantum level of electrons is different from the band edge side of the valence band in the well layer when viewed from the band edge of the conduction band. It exists over the entire area in the thickness direction of the well layer on the opposite side, but does not exist in the barrier layer except for slightly exuding from the well layer side. As in the case of the conventional semiconductor optical device described above with reference to FIG. 8, in the well layer, the thickness of the well layer is on the side opposite to the band edge side of the conduction band when viewed from the band edge of the valence band. Although it exists over the entire area in the depth direction, but does not exist in the barrier layer except for slightly exuding from the well layer side, the quantum level of the light hole is in the barrier layer, Snake hoo
It exists over the entire area in the thickness direction of the barrier layer on the side opposite to the band edge side of the valence band as seen from the quantum level of the electron, but slightly exudes from the barrier layer side in the well layer It doesn't exist except

For this reason, that is, since the active layer has the above-mentioned energy band structure, the signal light constitutes the single crystal semiconductor layer laminated body when the function as the semiconductor photodetector is obtained. When the signal light is absorbed in the active layer, the electrons are absorbed in the well layer when the signal light is in TE mode, as in the conventional semiconductor optical device described above with reference to FIG. In the case where the signal light is TM mode, the conventional semiconductor light described above with reference to FIG. 8 is generated by the transition between the electron quantum level and the heavy hole quantum level. Similar to the case of the device, even if electrons are generated in the well layer by a transition between the quantum level of the electron and the portion of the quantum level of the light hole that exudes in the well layer, In this case, the well layer exudes from the barrier layer side. As described above, the quantum level of ithole exists on the opposite side of the band edge side of the valence band from the viewpoint of the quantum level of the heavy hole existing in the well layer. Even if the quantum level of the light hole seeping out from the barrier layer side in the well layer exists only in the state localized in the well layer, the signal light is in TM mode. In this case, the probability that the electron transits from the quantum level of the electron to the quantum level of the light hole is higher than in the case of the conventional semiconductor optical device described above with reference to FIG. And the probability that the electron transits from the electron quantum level to the light hole quantum level, and when the signal light is in TE mode, the electron moves from the electron quantum level to the heavy hole There is little or no difference with the probability of transition to the quantum level. The difference is sufficiently small. Therefore, when the signal light is in the TM mode, the absorption coefficient is absorbed in the well layer, and when the signal light is in the TE mode, the absorption coefficient is absorbed in the well layer. There is little difference, or if there is a difference, the difference is small enough.

From the above, in the case of the semiconductor optical device according to the present invention, when it has a function as a semiconductor photodetector,
The photodetection sensitivity of the semiconductor photodetector hardly depends on whether the incident signal light is in TE mode or TM mode.

Further, according to the semiconductor optical device of the present invention, a plurality of semiconductor optical elements according to the first invention of the present application are provided.
Since the substrate is formed in common, each semiconductor optical element has the same effects as the semiconductor optical element according to the first aspect of the present invention.

[0031]

Embodiment 1 Next, an embodiment of the semiconductor optical device M according to the present invention will be described with reference to FIG.

In FIG. 1, parts corresponding to those in FIG. 8 are designated by the same reference numerals.

A semiconductor optical device M according to the present invention shown in FIG.
Is similar to the case of the conventional semiconductor optical device described above with reference to FIG.
A substrate 1 made of P, a single crystal semiconductor layer stack 2 formed on the substrate 1, and an electrode layer formed on the surface of the substrate 1 opposite to the single crystal semiconductor layer stack 2 side. 11 and
It has an electrode layer 12 formed on the surface of the single crystal semiconductor layer stack 2 opposite to the substrate 1 side.

In this case, the semiconductor layer laminated body 2 also has an n-type, which is formed by sequentially laminating from the substrate 1 side by the epitaxial growth method, as in the case of the conventional semiconductor optical device described above with reference to FIG. And a cladding layer 3 made of, for example, single crystal InP, and a guide layer 4 made of, for example, single crystal InGaAsP having an n-type and a lattice constant equal to that of single crystal InP as a single crystal semiconductor constituting the substrate 1.
An active layer 5 made of a single crystal semiconductor into which neither an n-type impurity nor a p-type impurity is intentionally introduced, and a single-crystal InP having a p-type and constituting the substrate 1 as a single-crystal semiconductor. Crystal InGaA having a lattice constant equal to
sP-based guide layer 6 and p-type and single crystal In
The clad layer 7 made of P and the cap layer 8 made of, for example, a single crystal InGaAsP system having a p-type and a lattice constant equal to that of single crystal InP as a single crystal semiconductor forming the substrate 1 are provided. The clad layer 3, the guide layer 4, the active layer 5, the guide layer 6, the clad layer 7 and the cap layer 8 have end faces 9a and 9b extending parallel to each other and facing each other in the stacking direction.

However, in the case of the semiconductor optical device according to the present invention shown in FIG. 1, the active layer 5 forming the single crystal semiconductor layer stack 2 is the single crystal InP as the single crystal semiconductor forming the substrate 1. Crystal I having a lattice constant equal to
A well layer 15a formed by an epitaxial growth method using a single crystal semiconductor made of nGaAs and a single crystal InGaAsP system having a smaller lattice constant than single crystal InP as the single crystal semiconductor forming the substrate 1 And a barrier layer 15b formed in a state in which tensile strain is applied in a direction orthogonal to the growth direction by an epitaxial growth method using a single crystal semiconductor of the following quantum well structure.

The above is the configuration of the embodiment of the semiconductor optical device M according to the present invention.

According to the semiconductor optical device M of the present invention having such a structure, as described in the conventional semiconductor optical device M described above with reference to FIG. 8 and as shown in the drawing, for example,
The electrode layer 12 is connected to the ground, and the electrode layer 11 is connected to the modulation signal S
Switching transistor Q that turns on and off by
Through the resistor R, and then to the negative power source E, and has two input terminals a and b having opposite polarities and one output terminal c, and the input terminal b is connected to ground. Output terminal c
Is connected to the input terminal b of the operational amplifier A having a configuration in which it is connected to the input terminal a through the feedback resistor R _f , and the switching transistor Q is turned off. For the active layer 5 forming the laminated body 2, the signal light L is formed by using an optical fiber (not shown) from either one of the opposite end faces 9a and 9b of the single crystal semiconductor layer laminated body 2. , The detailed description thereof will be omitted. However, as in the case of the conventional semiconductor optical device described above with reference to FIG. Since a photocurrent is generated, a photovoltage corresponding to the intensity of the signal light L is obtained at the output end c of the operational amplifier A, as in the case of the conventional semiconductor optical device described above with reference to FIG.

Therefore, the output terminal c of the operation amplifier A is the same as in the case of the conventional semiconductor optical device described above with reference to FIG. 8, as in the case of the conventional semiconductor optical device described above in FIG.
The signal light L can be detected by the optical voltage obtained in the above, and thus the function as a semiconductor photodetector can be obtained as in the case of the conventional semiconductor optical device described above with reference to FIG.

Further, according to the semiconductor optical device M of the present invention shown in FIG. 1, the electrode layers 11 and 12 are connected as shown in FIG. 11 as in the case of the conventional semiconductor optical device described in FIG. In this state, the switching transistor Q is on / off controlled by the modulation signal, and in the on section, from the power source E side through the electrode layers 11 and 12,
If a drive current is passed through the active layer 5 forming the semiconductor layered body 2, detailed description will be omitted. However, in the active layer 5, light is emitted in the same manner as in the conventional semiconductor optical device described in FIG. The generated light propagates in the active layer 5 toward the end faces 9a and 9b, and then is reflected by the end faces 9a and 9b.
The operation is repeated. Therefore, by appropriately selecting the distance between the end faces 9a and 9b of the single crystal semiconductor layer stack 2, laser oscillation occurs as in the case of the conventional semiconductor optical device described above with reference to FIG. The laser beam L'based on the laser oscillation can be emitted to the outside from either one of the end faces 9a and 9b. Therefore, the laser beam L'can be emitted from the conventional semiconductor optical device described above with reference to FIG. Similarly, the function as a semiconductor laser can be obtained.

Further, according to the semiconductor optical device M of the present invention shown in FIG. 1, the active layer forming the single crystal semiconductor layer stack 2 is the same as in the conventional semiconductor optical device described in FIG. Since 5 has a quantum well structure in which well layers 15a and barrier layers 15b are alternately laminated in sequence, the function as the semiconductor photodetector and the function as the semiconductor laser described above are described in FIG. Similar to the case of the conventional semiconductor optical device, the active layer 5 does not have such a quantum well structure and can be effectively obtained as compared with the case of a single layer structure.

In the case of the semiconductor optical device M according to the present invention shown in FIG. 1, the cladding layer 3 constituting the single crystal semiconductor layer stack 2 is the same as in the conventional semiconductor optical device described in FIG. Are formed by an epitaxial growth method using the same single crystal InP as the single crystal semiconductor constituting the substrate 1 and the guide layer 4 is formed on the substrate 1.
Is formed by an epitaxial growth method using a single crystal InGaAsP system having a lattice constant equal to that of the single crystal InP as the single crystal semiconductor constituting the substrate 1. Therefore, the cladding layer 3 and the guide layer 4 have the same lattice as the substrate 1. Have an array.

However, in the case of the semiconductor optical device M according to the present invention shown in FIG. 1, the active layers 5 constituting the single crystal semiconductor layer stack 2 are formed by alternately stacking well layers 15a and barrier layers 15b. 2, the well layer 15a is made of a single crystal InGaAs system having a lattice constant equal to that of single crystal InP as a single crystal semiconductor forming the substrate 1, as shown in FIG. Although the barrier layer 15b is formed by the epitaxial growth method using the single crystal semiconductor 15a ', the barrier layer 15b is a single crystal InGaAsP system having a smaller lattice constant than single crystal InP as the single crystal semiconductor forming the substrate 1. Is formed in a state in which tensile strain is applied in the direction orthogonal to the growth direction by the epitaxial growth method using the single crystal semiconductor Well layer 5a, as in the case of the conventional semiconductor optical device described above in FIG. 8, in the state in which any tensile strain in the direction perpendicular to the growth direction is not given as it is formed by the epitaxial growth method, the substrate 1
The substrate 1 has the same lattice arrangement as that of the substrate 1 while the barrier layer 15b is subjected to tensile strain in the direction orthogonal to the growth direction when the barrier layer 15b is formed by the epitaxial growth method.
It has the same lattice arrangement as.

In the case of the semiconductor optical device M according to the present invention shown in FIG. 1, the barrier layer 5b forming the active layer 5 of the single crystal semiconductor layer stack 2 is formed by the epitaxial growth method as described above. Since the active layer 5 has the same lattice arrangement as the substrate 1 in the state where tensile strain is applied in the direction orthogonal to the growth direction at that time, the active layer 5 has the energy band structure described below.

That is, as shown in FIG. 3, unlike the conventional semiconductor optical device M described with reference to FIG.
Since the barrier layer 15b forming the structure has a tensile strain, the band edge of the conduction band and the band edge of the valence band are the same as in the case of the conventional semiconductor optical device described above with reference to FIG. In addition, the well layers 15a forming the active layer 5 have one each and the conduction band edge is one in the barrier layer 15b. In the layer 15b, there are two ends, that is, a light-holed band edge and an underlying heavy-hole band edge.

Therefore, the quantum level E _c of the electron is the same as in the conventional semiconductor optical device described above with reference to FIG.
5a is present over the entire region in the thickness direction of the well layer on the side opposite to the band edge side of the valence band as seen from the band edge of the conduction band, but in the barrier layer 15b from the well layer side. It does not exist except that it slightly exudes, and the quantum level E _hh of the _heavy hole is in the well layer 15a in the same manner as in the conventional semiconductor optical device described above with reference to FIG. On the side opposite to the band edge side of the conduction band as seen from the band edge of the valence band, the well layer 15a is present over the entire region in the thickness direction, but in the barrier layer 15b it is slightly from the well layer 15a side. Although it does not exist except that it oozes out, the quantum level E _lh of the light hole is present in the barrier layer 15b in the snake.
On the side opposite to the band edge side of the valence band as seen from the quantum level E _{hh of the} holes, the barrier layer 15b is present over the entire region in the thickness direction, but the barrier layer is present in the well layer 15a. 1
It does not exist except that it slightly exudes from the 5b side.

For this reason, that is, since the active layer 5 has the above-mentioned energy band structure, the signal light L has the single crystal semiconductor layer laminated body 2 when it functions as a semiconductor photodetector. When the signal light L is absorbed by the active layer 5 constituting the
In the well layer 15a, the electron quantum level E _c and the heavy hole quantum level E _hh are generated in the well layer 15a, as in the conventional semiconductor optical device M described above with reference to FIG. Between the signal light L and the TM mode.
8 is similar to the case of the conventional semiconductor optical device M described above with reference to FIG. 8, the electrons in the well layer 15a have the quantum level E _c of the electron and the quantum level E _lh of the light hole. In this case, the quantum level E _lh of the light hole exuding from the barrier layer 15b side in the well layer 15a is equal to As described above, since the heavy hole exists in the well layer 15a on the side opposite to the band edge side of the valence band as seen from the quantum level E _{hh of the} heavy hole, the well layer 1
Even if the quantum level E _lh of the light hole exuding from the barrier layer 15b side in 5a exists only in the state in which it is localized in the well layer 15a, the signal light L is TM mode. The probability that an electron transits from the quantum level E _{c of the} electron to the quantum level E _lh of the light hole in the case of the charge mode is higher than that in the case of the conventional semiconductor optical device M described above with reference to FIG. , When the signal light L is in TM mode, the probability that an electron transits from the electron quantum level E _c to the light hole quantum level E _lh , and when the signal light L is in TE mode There is almost no difference between the electron's quantum level E _c and the probability of transition to the _heavy hole quantum level E _hh , or if there is a difference, the difference is sufficiently small. Therefore, when the signal light L is in the TM mode, it is absorbed in the well layer 15a, and when the signal light L is in the TE mode, it is absorbed in the well layer 15a.
There is almost no difference with the absorption coefficient, or even if there is a difference, the difference is sufficiently small.

From the above, in the case of the semiconductor optical device M according to the present invention shown in FIG. 1, when it has a function as a semiconductor photodetector, the photodetection sensitivity of the semiconductor photodetector is that of the incident signal light. Is in the TE mode or the TM mode, and therefore, it hardly depends on the polarization mode of the signal light L.

This means that the same signal light L is used in the case of the semiconductor optical device M according to the present invention shown in FIG. 1 and the case of the conventional semiconductor optical device M described in FIG. Of 10 _log10 (I _min / I _max ) (where I
_max and I _min , while rotating the polarization plane of the signal light L,
Polarization dependence defined as (maximum value and minimum value of the photocurrent when the photocurrent flowing to the outside through the electrodes 11 and 12) was measured by changing the wavelength. The results shown (expressed in dB) were obtained, and
The light detection sensitivity of the semiconductor optical device according to the present invention shown in FIG.
_Assuming that it is represented by I _{max as} described above, it will be apparent from the fact that the I _max was measured and the result shown in FIG. 5 (expressed in dB) was obtained.

Further, according to the semiconductor optical device M of the present invention shown in FIG. 1, when the function as the semiconductor laser described above is obtained, the optical output (mW) by the laser beam with respect to the drive current (mA) is obtained. ) Was measured, and FIG.
As shown in, the driving current threshold of 20 nA is 1550 nm.
The result obtained is that when a laser beam having a wavelength of 1 is generated and the driving current is 30 mA, an optical output of 5 mW is obtained.

[0050]

[Embodiment 2] Next, an embodiment of a semiconductor optical device according to the present invention using the semiconductor optical element according to the present invention will be described with reference to FIG.

The semiconductor optical device according to the present invention shown in FIG.
In the semiconductor optical device M according to the present invention described above with reference to FIG. 1, a groove is formed in the semiconductor optical device M from the electrode layer 12 side to reach the substrate 1 across the single crystal semiconductor layer stack 2.
A plurality of semiconductor optical devices M ₁ , M ₂ ... _Mn and a plurality of semiconductor optical devices M ₁ ′, M ₂ ′ ... M _n ′ are provided.
The substrate 1 is commonly used and the semiconductor optical devices M _i and M _i ′ (where i = 1, 2, ..., N) are collinearly arranged so that one end face 9 b of the former and one end face 9 a of the latter face each other. It is formed by arranging in an array.

The above is the configuration of the embodiment of the semiconductor optical device according to the present invention.

According to the semiconductor optical device of the present invention having such a configuration, a plurality of n semiconductor optical elements M _{1 to} M _{n are provided.}
Of the semiconductor optical device M according to the present invention shown in FIG.
Since it has the same configuration as the above, a plurality n of semiconductor optical devices M
For each of _{1 to} M _n , the same as in the case of the semiconductor optical device according to the present invention shown in FIG. 1 with or without each of the corresponding optical fibers F _{1 to} F _n as shown. together it is clear that the advantages are achieved, semiconductor laser by a semiconductor optical device M _i - when obtaining the function as the a portion of the light from the semiconductor optical device M _i to the semiconductor optical device M _i ' The semiconductor optical device M _i ′ can be made incident and the operation of the semiconductor optical device M _i can be monitored.

In the above description, for each of the semiconductor optical device and the semiconductor optical device according to the present invention, 1
Only one embodiment is shown, and various modifications and changes can be made without departing from the spirit of the present invention.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an embodiment of a semiconductor optical device according to the present invention.

FIG. 2 is a view showing an active layer of the semiconductor optical device according to the present invention shown in FIG.

FIG. 3 is a diagram showing the mechanism of signal light absorption in the active layer of the semiconductor optical device according to the present invention shown in FIG. 1, together with the energy band structure of the active layer.

4 shows the polarization dependency of an optical signal with respect to the wavelength of the optical signal when the function as a semiconductor photodetector is obtained by the semiconductor optical device according to the present invention shown in FIG. It is a figure which shows in comparison with the polarization dependence of the optical signal with respect to the wavelength of an optical signal when the function as a detector is acquired.

5 is a diagram showing photodetection sensitivity with respect to wavelength when a function as a photodetector is obtained by the semiconductor optical device according to the present invention shown in FIG.

FIG. 6 is a diagram showing a relationship between a drive current and an optical output when the semiconductor optical device according to the present invention shown in FIG. 1 obtains a function as a semiconductor laser.

FIG. 7 is a schematic plan view showing an embodiment of a semiconductor optical device according to the present invention.

FIG. 8 is a schematic cross-sectional view showing a conventional semiconductor optical device.

9 is a diagram showing an active layer of the conventional semiconductor optical device shown in FIG.

10 is a diagram showing the mechanism of signal light absorption in the active layer of the conventional semiconductor optical device shown in FIG. 8 together with the energy band structure of the active layer.

11 is a diagram showing a circuit for obtaining a function as a semiconductor photodetector and a function as a semiconductor laser by the semiconductor optical device according to the present invention shown in FIG. 1 and the conventional semiconductor optical device shown in FIG. is there.

[Explanation of reference numerals] 1 substrate 2 single crystal semiconductor layer stack 3 clad layer 4 guide layer 5 active layer 5a well layer 5b barrier layer 6 guide layer 7 clad layer 8 cap layer 9a, 9b end face 11, 12 electrode layer 15a well layer 15b barrier layer A amplifier _{M, M 1 ~M n, M} 1 '~M n' semiconductor optical device Q switching transistor

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 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Mitsuo Fukuda 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation (72) Minoru Okamoto 1-16-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Toshihiko Sugie 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation (72) Inventor Hiroyasu Madawa 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation

Claims (2)

[Claims] 1. A semiconductor optical device having a substrate made of a single crystal semiconductor and an active layer made of a single crystal semiconductor formed on the substrate, wherein the active layer is a single crystal constituting the substrate. A well layer formed by an epitaxial growth method using a single crystal semiconductor having a lattice constant equal to that of the semiconductor, and an epitaxial growth method using a single crystal semiconductor having a smaller lattice constant than the single crystal semiconductor forming the substrate. 2. A semiconductor optical device having a quantum well structure in which barrier layers formed in a state in which tensile strain is applied in a direction orthogonal to the growth direction of the quantum well structure are sequentially stacked alternately. 2. A semiconductor optical device having a plurality of semiconductor optical devices formed by using a substrate made of a single crystal semiconductor, each of the plurality of semiconductor optical devices being made of a single crystal semiconductor formed on the substrate. And a well layer in which each active layer of the plurality of semiconductor optical devices is formed by an epitaxial growth method using a single crystal semiconductor having a lattice constant equal to that of the single crystal semiconductor forming the substrate, and A barrier formed in a state in which a tensile strain is applied in a direction orthogonal to the growth direction by an epitaxial growth method using a single crystal semiconductor having a lattice constant smaller than that of the single crystal semiconductor forming the substrate. A semiconductor optical device having a quantum well structure in which layers are sequentially stacked alternately.