JPH05343810A - Semiconductor laser - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a multi-beam semiconductor laser having a structure that suppresses thermal crosstalk (mutual thermal interference) during driving. A first clad layer 12, an active layer 13, and a second clad layer 14 are grown at least in this order on a GaAs substrate 10 having a low thermal resistance to form two laser resonators having an independent drive structure. , Current blocking layer 16
A dielectric such as Si ₃ N ₄ or SiO ₂ having high thermal resistance,
Alternatively, it is formed of a mixed crystal of AlInP, AlGaInP, etc., and has a larger thermal resistance than the conventional GaAs mixed crystal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser,
In particular, the present invention relates to a multi-beam semiconductor laser formed by forming a plurality of laser resonators each having an independently driven structure in a laser chip.

[0002]

2. Description of the Related Art Recently, multi-beam semiconductor lasers have been used as high-power light sources for laser printers, optical disks, and the like. This kind of multi-beam semiconductor laser has a plurality of laser resonators of independent drive structure in the laser chip, unlike a semiconductor laser that simultaneously drives a plurality of laser resonators with a common electrode for higher output. ..

FIG. 6 is a sectional view of a chip of a multi-beam semiconductor laser of this type, which shows a first buffer layer 11, a first cladding layer 12 and an active layer 1 on a semiconductor substrate 10.
3, the second clad layer 14 and the second buffer layer 15 are formed in this order, and the second buffer layer 15 and the second clad layer 14 are mesa-etched to form a plurality of stripes (two in FIG. 6). It forms an area. These stripe regions are separated by current blocking layers 16a to 16c at predetermined intervals, and contact layers 18a and 18b separated by a resist layer 17 are formed on the surfaces of these layers.
The p-electrode 19 is formed on the upper surfaces of the contact layers 18a and 18b.
a, 19b, the common n-electrode 19c on the bottom surface of the semiconductor substrate 10
Are formed. The first and second buffer layers 1
1 and 15 are the semiconductor substrate 10 and the second cladding layer 1, respectively.
There is also a structure that is integrated with 4 and does not exist independently.

In the above structure, conventionally, usually, n-type (first conductivity type, the same applies hereinafter) GaAs mixed crystal in the semiconductor substrate 10, n-type III-V atom mixed crystal in the first cladding layer 12, and the active layer. 13 is an undoped III-V mixed crystal, the second cladding layer 14 is a p-type (second conductivity type, hereinafter the same) III-V mixed crystal, and the current block layer is a GaAs mixed crystal. ..

In the multi-beam semiconductor laser having such a structure, when a current is passed in the vertical direction of FIG. 7, the p-electrode 19a,
Carriers from 19b are the current blocking layers 16a to 16c.
The second cladding layer 14 is moved through the upper surface of each stripe region. At that time, the carrier
An electric field causes a beam-like distribution from the second clad layer 14 to the n common electrode 19c across the active layer 13 and the first clad layer 12. Therefore, current flows in the width on the upper surface of each stripe region, and the active layer 1 corresponding to each current width is formed.
Laser oscillation is independently performed in the region of 3. That is, an independently drivable laser resonator is formed for each stripe region.

[0006]

By the way, one of the problems in driving a multi-beam semiconductor is thermal crosstalk. This is because, for example, in a multi-beam semiconductor laser having two laser resonators as shown in FIG. 6, when one laser resonator is driven to emit a beam, the other laser resonator is driven. The heat generated by energization is conducted to one of the laser resonators, and the beam output level is lowered.

In the case of the conventional multi-beam semiconductor laser, since the driving current is large and the thermal resistance is relatively large, heat conduction easily occurs between the laser resonators. Therefore, the output level of the beam emitted from each laser resonator fluctuates significantly, resulting in a decrease in operational reliability. To avoid the effects of this thermal crosstalk,
There has been a limit in reducing the manufacturing cost because it is necessary to increase the formation interval of the laser resonators and to arrange a member that blocks heat conduction between the laser resonators.

The present invention has been made under such a background, and an object thereof is to provide a semiconductor laser having a structure capable of effectively preventing thermal crosstalk.

[0009]

According to the present invention, in a semiconductor laser having a conventional structure, the current blocking layer is made of a conventional Ga material.
Replaced with As mixed crystal, Si ₃ with larger thermal resistance than this
Dielectrics such as N ₄ and SiO ₂ , or AlGaIn
It is characterized by being formed of a semiconductor mixed crystal made of either P or AlInP.

[0010]

The dielectric crystal such as Si ₃ N ₄ , SiO ₂ or the mixed crystal of AlInP and AlGaInP is GaAs.
Greater thermal resistance than mixed crystals. Therefore, when these materials are used for the current blocking layer, the heat generated in the laser resonator by energization becomes difficult to be conducted to the adjacent laser resonator via the current blocking layer. As a result, in the laser, the heat transferred to the adjacent resonator via the current blocking layer side of the active layer is suppressed, so that the total amount of heat transferred to the adjacent resonator is reduced. Therefore, by adopting the crystal structure of the present invention, the thermal conductivity between the laser resonators becomes smaller than in the conventional case, and the influence of thermal crosstalk is mitigated.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. Since the present invention is one in which the composition of the layer crystal of the conventional multi-beam semiconductor laser is changed, the description will be made using the same names and reference numerals of the respective layers.

A multi-beam semiconductor laser according to an embodiment of the present invention has the conventional layer structure shown in FIG. 6 in which the current blocking layer 16 is formed of Si ₃ N ₄ dielectric.

One means for suppressing the thermal crosstalk of the multi-beam semiconductor laser is to improve the heat dissipation from the laser chip and reduce the temperature rise due to heat generation. According to this idea, it seems to be a disadvantage to use a Si ₃ N ₄ dielectric having a thermal resistance higher than that of a conventional GaAs mixed crystal. However, according to the consideration of the present inventors,
Considering the heat conduction path, it has been found that the fact that the thermal resistance of the current blocking layer is rather large is advantageous. That is,
As shown in FIG. 1, the heat generated in the active layer when the laser resonator is driven is suppressed in the semiconductor laser by the current block layer made of a dielectric material having a large thermal resistance via the current block layer side of the active layer. To be done. Therefore, the amount of heat conducted to the adjacent resonator is smaller than in the conventional case, and the thermal crosstalk is reduced accordingly.

In the above, the current blocking layer 16 is made of Si ₃
Although it is formed of N ₄ dielectric, in addition to that, S
The same effect can be obtained when formed of a dielectric material such as iO ₂ or polymide.

FIG. 2 is a sectional view of the layer structure of a laser epi which is a starting material for the multi-beam semiconductor laser of the present embodiment. Referring to FIG. 2, a first buffer layer 11 having a thickness of 0.23 [μm] and a thickness of 1.1 is formed on the upper surface of the semiconductor substrate 10.
[Μm] first cladding layer 12, strained quantum well layer 13a
˜13 g of the active layer portion 13, the 1.1 [μm] thick second clad layer 14, and the 0.14 [μm] thick second buffer layer 15 are OMVPE (Organometallic v).
It is formed in this order by a well-known crystal growth means such as an apor phase epitaxy method.

These semiconductor substrate 10 and layers 11 to 15
Of these, the semiconductor substrate 10 has an electron concentration of 2 × 10 ¹⁸ [cm
^-3 ] Si-doped GaAs mixed crystal, first buffer layer 1
1 is an Si-doped GaAs mixed crystal having an electron concentration of 1.5 × 10 ¹⁸ [cm ⁻³ ], and the first cladding layer 12 has an electron concentration of 2
× 10 ¹⁷ [cm ⁻³ ] Se-doped (Al _0.7 G
a _0.3 ) In _0.5 P mixed crystal, and the active layer portion 13 includes undoped (Al _0.4 ) 13a and 13g having a thickness of 0.08 [μm].
Ga _0.6 ) _0.5 In _0.5 P layer, 13c and 13e are undoped (Al _0.4 Ga _0.6 ) with a thickness of 0.008 [μm]
_0.5 In _0.5 P layers, 13b, 13d, 13f having a thickness of 0.
Ga _0.43 In _0.57 P layer of 01 [μm], and the second cladding layer 14 is a Zn-doped (Al _0.7 Ga _0.3 ) In _0.5 P mixed crystal having a hole concentration of 4 × 10 ¹⁷ [cm ⁻³ ] Of the buffer layer 15 are made of Zn-doped Ga _0.5 In _0.5 P mixed crystal having a hole concentration of 1 × 10 ¹⁸ [cm ⁻³ ].

3 to 5 are manufacturing process diagrams of the multi-beam (double-beam) semiconductor laser of this embodiment. Less than,
Each step will be described with reference to these drawings.

First, using the laser epi as a starting material (see FIG. 3A), a resist film 20 is formed on the upper surface of the second buffer layer 15, and then a resist 21 is patterned (FIG. 3B). reference). Then, the resist film 20 other than the portion covered with the resist 21 is etched, and then the resist 21 is removed (see (c) of the same). This is mixed with acid at 50 ° C. (sulfuric acid: hydrogen peroxide: water = 3: 1:
Etching is performed in 1) for 6 minutes, and the second cladding layer 14 is left by about 0.2 μm (see (d)). This allows
Two stripe regions are formed.

Next, a Si ₃ N ₄ dielectric film is added to 0.3 [μ
m] After the growth, the remaining resist film 20 is etched. Thereby, the current block layers 16a to 16c are formed (see FIG. 4A). Then, the current blocking layer 1
A resist film 22 is formed on the surfaces of 6a to 16c and each stripe region, and a resist 23 is placed in the center of the resist film 22 (see (b)). Then, the resist film 22 other than the portion on which the resist 23 is placed is etched (see (c) in the above), and Zn-doped GaAs (hole concentration 4 × 10 ¹⁷ [c] is formed on the upper surface thereof.
m ⁻³ ]) for 1 [μm] growth. As a result, the contact layers 18a and 18b are formed (see (d)).

The resist film 22 in the central portion is removed, and an insulating film 24 is newly formed on the entire surfaces of the contact layers 18a and 18b. A resist 25 is patterned in the central portion (see FIG. 5A). After that, the contact layers 18a and 18b
The insulating film 24 on the upper surface is etched (see the same (b)), and the p electrode member 26 is vapor-deposited on the entire surface (see the same (c)). The resist 25 is removed, and at the same time, the p electrode member 26 on the upper surface of the resist 25 is removed.
Also remove. As a result, p electrodes 19a and 19b are formed. Furthermore, the substrate 10 is etched from the back to 70 [μ
m]. Then, the n common electrode 1 is formed on the back surface of the substrate 10.
9c is vapor-deposited and alloyed at 400 ° C./1 min in a nitrogen atmosphere (see (d)).

Next, another embodiment of the present invention will be described. The structure of this semiconductor laser is almost the same as that of the above-mentioned embodiment, and only the composition of the current blocking layer is different. That is, in FIG. 6, the current blocks 16a to 16c are replaced with AlIn.
It was formed of a mixed crystal of P or AlGaInP. By changing the material of the current blocking layer and going through the steps of FIGS. 3 to 5 as in the above-described embodiment, a multi-beam semiconductor laser with small thermal crosstalk can be obtained.

[0022]

As described above in detail, in the present invention, in the semiconductor laser using the GaAs substrate, the current blocking layer is made of Si ₃ N ₄ and SiO ₂ having high thermal resistance.
Since it is formed of a dielectric such as or a semiconductor mixed crystal of GaInP and AlGaInP, the thermal conductivity between the laser resonators is smaller than that of the semiconductor laser of the conventional structure, and the thermal crosstalk is reduced.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a heat transfer path of a multi-beam semiconductor laser.

FIG. 2 is a sectional view of a layer structure of a laser epi according to an embodiment of the present invention.

FIG. 3 is a manufacturing process diagram of the multi-beam semiconductor laser of the present embodiment.

FIG. 4 is a manufacturing process diagram of the multi-beam semiconductor laser of the present embodiment (continuation of FIG. 3).

FIG. 5 is a manufacturing process diagram of the multi-beam semiconductor laser of the present embodiment (continuation of FIG. 4).

FIG. 6 is a sectional view of a layer structure of a general multi-beam semiconductor laser to which the present invention is applied.

[Explanation of symbols]

10 ... Semiconductor substrate, 12 ... First clad layer, 13 ... Active layer, 14 ... Second clad layer, 16a-16c ... Current blocking layer, 19a-19c ... Electrode.

Claims (3)

[Claims] 1. A first conductivity type GaAs substrate, at least a first clad layer of a first conductivity type semiconductor mixed crystal, an active layer of a semiconductor mixed crystal, and a second cladding of a second conductivity type semiconductor mixed crystal. Layers are formed at least in this order, and further, the surface of the second clad layer is formed into a plurality of stripe regions separated by a current block layer at predetermined intervals, and a plurality of laser resonators having an independent drive structure are formed. A semiconductor laser, wherein the current blocking layer is formed of a dielectric material. 2. The semiconductor laser according to claim 1, wherein the dielectric material is one of silicon nitride and silicon oxide. 3. A first conductivity type GaAs substrate, at least a first clad layer of a first conductivity type semiconductor mixed crystal, an active layer of a semiconductor mixed crystal, and a second cladding of a second conductivity type semiconductor mixed crystal. Layers are formed at least in this order, and further, the surface of the second clad layer is formed into a plurality of stripe regions separated by a current block layer at predetermined intervals, and a plurality of laser resonators having an independent drive structure are formed. In the semiconductor laser, the current blocking layer is formed of a semiconductor mixed crystal of AlGaInP or AlInP.