KR20140035045A - Algainp light emitting diode with n-type gan window layer and preparation thereof - Google Patents

Abstract

The present invention relates to a light emitting diode and a method of manufacturing the same, and more particularly, to growing a window layer on an n-type limiting layer which is the uppermost layer of an AlGaInP light emitting diode that is wafer-bonded or grown on a p-type substrate. The AlGaInP light emitting diode according to the present invention is characterized in that an n-type GaN window layer is grown on the n-type limiting layer. The n-type GaN window layer enlarges a light emitting region by current diffusion and a light emitting region by securing an upper emitting cone region, thereby greatly increasing the efficiency of the light emitting diode.

Description

Technical Field The present invention relates to an aluminum gallium indium phosphide light emitting diode having a gallium nitride window layer and an aluminum gallium indium phosphide light emitting diode having a gallium nitride gallium window layer,

The present invention relates to a light emitting diode and a method of manufacturing the same, and more particularly, to growing a window layer on an n-type limiting layer which is the uppermost layer of an AlGaInP light emitting diode that is wafer-bonded or grown on a p-type substrate.

AlGaInP light emitting diodes are semiconductor devices that convert the injected electrical energy into light with a specific wavelength within the range of about 570-630 nm. The change of the specific wavelength depends on the size of the band gap of the light emitting diode. The band gap size can be easily controlled by changing the composition ratio of aluminum (Al) and gallium (Ga). For example, As the value increases, the wavelength becomes shorter.

In general, an AlGaInP light-emitting diode is manufactured by growing an AlGaInP-based material into a double heterostructure on an n-type GaAs substrate having a matching lattice constant by using a metal organic chemical vapor deposition (MOCVD) system capable of growing a high quality thin film . The AlGaInP light emitting diode has a structure composed of an undoped AlGaInP-based high-efficiency active layer calculated at a specific wavelength in the middle of an n-type AlGaInP material layer (n-type limiting layer) and a p-type AlGaInP material layer (p-type limiting layer). Since the active layer, the n-type limiting layer and the p-type limiting layer have a relatively high resistance, most of the layers are grown to a thickness of less than 1 μm (total thickness <3 μm) in consideration of a general-purpose light emitting diode. In order to increase the current diffusion effect between the upper electrode and the active layer, a window layer made of a GaP or AlGaAs material is usually grown on the upper part. These materials have a relatively high conductivity and a high bandgap compared to an AlGaInP- Thereby increasing the efficiency of the light emitting diode without affecting the intrinsic characteristics of the light emitting diode.

Such AlGaInP light emitting diodes are generally inefficient because the light emitted from the active layer toward the lower substrate is mostly absorbed by the thick GaAs substrate having a small bandgap. Even if a dispersed Bragg reflector (DBR) is grown between an absorbing GaAs substrate and an AlGaInP-based material, the effect is small because it is reflected by the DBR only when the incident angle is almost perpendicular.

In general, a high-efficiency AlGaInP light-emitting diode is obtained by inserting a reflection film that efficiently reflects light to be absorbed on a lower substrate in an upward direction, and insertion of the reflection film is made by a technique called wafer bonding.

1 shows a general low-efficiency AlGaInP light-emitting diode (Absorbing Substrate LED) and a right-side view shows a wafer bonding AlGaInP light-emitting diode (Mirror Substrate LED) having a reflection film. During the wafer bonding for the production of a high efficiency AlGaInP light emitting diode having a reflective film, the AlGaInP system including the p-type GaP window layer is reversed to the structure of the n-type AlGaInP system at the top. Figure 1 (b) shows the reversal of this structure.

The structural reversal phenomenon in the fabrication of high - efficiency AlGaInP light - emitting diodes makes the grown GaP or AlGaAs layer no longer serve as a window to increase the current diffusion efficiency of the light emitting diode. As a result, the wafer-bonding type AlGaInP light emitting diode manufactured to date has no window layer, and the efficiency of the wafer bonding-type AlGaInP light emitting diode is limited due to the limited light emitting region of the active layer.

The present invention relates to a method of growing an n-type window layer on an AlGaInP light emitting diode or a p-type substrate grown on a wafer bonding AlGaInP light emitting diode, thereby increasing the efficiency of the light emitting diode .

The present invention is characterized in that an n-type GaN window layer is grown on an n-type limiting layer in an AlGaInP light emitting diode grown on a wafer bonding type AlGaInP light emitting diode or a p-type substrate. The n-type GaN window layer is preferably formed by vapor deposition, more preferably by MOCVD.

In the present invention, the term "wafer bonding type AlGaInP light emitting diode" refers to an AlGaInP light emitting diode to which a wafer bonding technique for inserting a reflective film for increasing the efficiency of a light emitting diode is applied. The AlGaInP light emitting diode to which the wafer bonding technique is applied is, for example, an n-type limiting layer which is grown on an n-type substrate, inverted upward. Wafer bonding techniques are well known in the art and will not be described in detail here.

In the present invention, the n-type GaN material used as the window layer is transparent and has a smaller resistance than the underlying AlGaInP-based material. The term &quot; transparent &quot; as used herein means that a band gap is relatively larger than that of an AlGaInP material so as to transmit light without absorbing light emitted from the active layer. The bandgap of the GaN material is about 3.2 eV, while the bandgap of the Al _x Ga _{1 -x) 1-y} In _y P material is about 1.7-2.3 eV, depending on the x value.

In the present invention, the n-type GaN window layer is preferably made of n-type GaN doped with disilane (Si ₂ H ₆ ), but the dopant is not limited thereto. Generally, since the p-type GaN layer is difficult to be doped because it is difficult to be used as a window layer due to its high resistance, the n-type GaN layer can be formed into a window layer having a small resistance because of its good doping. The resistivity of the n-type GaN layer is about 0.005? Cm, which is about 200 times smaller than the resistivity of the AlGaInP material (about 1? Cm).

It is preferable that the n-type GaN window layer is formed in a concavo-convex shape in order to increase the light extraction efficiency by reducing the total reflection amount which is an obstacle to the emission of light from the active layer to the outside of the light emitting diode. As used herein, the term &quot; concavo-convex &quot; means that a fine concavo-convex pattern is formed on the surface, and can be understood to have a rough surface property.

In one aspect of the present invention, a method of manufacturing an AlGaInP light emitting diode includes: growing an n-type limiting layer, an active layer, and a p-type limiting layer on an n-type substrate; Optionally growing a p-type window layer over the p-type confinement layer; Forming a reflective layer structure on the grown uppermost layer, bonding to a p-type substrate, and removing the n-type substrate; And growing an n-type GaN window layer on the n-type limiting layer.

In one aspect of the present invention, a method of manufacturing an AlGaInP light emitting diode includes the steps of growing a p-type limiting layer, an active layer, and an n-type limiting layer on a p-type substrate; And growing an n-type GaN window layer on the n-type limiting layer.

In the present invention, the n-type GaN window layer may be grown to form a concave-convex pattern on the surface by being deposited in a high-doping environment.

The n-type GaN layer grown on the n-type limiting layer of the AlGaInP light emitting diode according to the present invention functions as a window layer to enlarge a light emitting region by current diffusion and a light emitting region by securing an upper emitting cone region, Can be greatly increased.

In addition, since the n-type GaN window layer can be formed by surface irregularities during its growth by doping control, the light extraction efficiency can be improved by forming a light scattering surface without additional process or cost such as chemical etching treatment.

The n-type GaN window layer has a high bandgap and low resistance, thereby increasing the efficiency of the light emitting diode without affecting the voltage-current characteristics of the AlGaInP light emitting diode.

FIG. 1 schematically shows an AlGaInP light emitting diode structure according to the prior art, wherein (a) shows an absorber plate type (AS) light emitting diode and (b) shows a mirror plate type (MS) light emitting diode.
FIG. 2 (a) shows a wafer-bonding type AlGaInP light emitting diode according to the related art, and FIG. 2 (b) shows an AlGaInP light emitting diode having an n-type GaN window layer according to an embodiment of the present invention.
Fig. 3 (a) is an electron micrograph of a AlGaInP light emitting diode having a concave-convex n-type GaN window layer according to the present invention, and Fig. 3 (b) (C) is a graph showing quantitative analysis data for a part of the photograph (a). Fig.

Additional aspects, features, and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. In order to facilitate a clear understanding of the present invention, some of the elements in the figures may be exaggerated, omitted or schematically illustrated. Also, the size of each component does not entirely reflect the actual size.

FIG. 2 is a cross-sectional view of a conventional AlGaInP light emitting diode (a) and a wafer bonding AlGaInP light emitting diode according to an embodiment of the present invention. The AlGaInP light emitting diode (b) 2 is a simplified schematic diagram of the structure.

The wafer bonding type AlGaInP light emitting diode (a) includes an n-type AlGaInP limiting layer 3, an AlGaInP active layer 4, a p-type AlGaInP limiting layer 5, a p-type GaP or AlGaAs The reflective layer 8 and the ohmic solder layer 9 are deposited on the uppermost layer 6 of the epi layer 6 and then the ITO layer 7 and the ohmic solder layer 9 are deposited on the uppermost layer 6 of the epi layer, The upper electrode 1 and the lower electrode 11 are provided after the n-type GaAs substrate is removed by bonding to the p-type Si substrate 10 on which the soldering layer as the bonding material is deposited. Therefore, the light emitting diode (a) has a layer structure in which the n-type AlGaInP limiting layer (3) moves to the top.

In the wafer bonding type light emitting diode a, the ITO 7, the reflective layer 8 and the soldering layer 9 have a lower reflective film structure. This is because most of the light emitted from the active layer 4 toward the lower substrate 10 And reflects upward. More specific manufacturing processes such as the process conditions of the wafer bonding type AlGaInP light emitting diode (a) can be performed according to a manufacturing technique of an AlGaInP light emitting diode known in the art.

As described above, the conventional wafer bonding AlGaInP light emitting diode (a) has a structure in which no window layer is present on the upper part. According to an embodiment of the present invention, an n-type GaN window layer is stably grown on the n-type AlGaInP confinement layer 3 which is the uppermost layer of the light emitting diode (a) by MOCVD, thereby forming a new AlGaInP based light emitting diode b ) Can be produced.

The n-type GaN window layer is grown at a relatively low temperature, preferably about 400 to 700 ° C, more preferably about 500 to 600 ° C, in the MOCVD system at a temperature lower than that of the growth of the AlGaInP material.

The n-type GaN window layer 2 may be grown so that the surface of the n-type GaN window layer 2 has a concavo-convex shape. Such a concavo-convex form can be simply formed by performing a high doping treatment in a part of the upper section during growth of the window layer 2. The high doping process can be defined to set the flow rate of the dopant, such as disilane (Si ₂ H ₆ ), to be preferably greater than or equal to about 60 sccm, and more preferably greater than or equal to about 80 sccm. As the flow rate of the dopant or precursor gas increases, the surface tends to be more coarse. In the MOCVD system, a high-quality n-type GaN window layer having a rough surface can be grown by growing a n-type GaN layer with a predetermined thickness and then growing a highly doped n ++ -type GaN layer.

When the n-type GaN window layer 2 is formed in a concavo-convex shape, light emitted upward from the active layer 4 is totally reflected at the surface boundary of the uppermost layer, It is possible to reduce the heading toward the inside.

Since the n-type GaN window layer has a very small resistivity, the current spreading effect and the enlargement of the upper side emission cone region can be achieved without affecting the voltage-current characteristics even if the thickness is increased to several to several tens of micrometers.

FIG. 3 is an electron micrograph of an AlGaInP light emitting diode having an uneven n-type GaN window layer manufactured according to the present invention, wherein (a) is a photograph showing the upper surface and (b) (C) is a side view showing the GaN window layer, and (c) shows quantitative analysis data on a part of the surface photograph (a).

The n-type GaN window layer having irregularities on its surface was formed by depositing disilane (Si ₂ H ₆ ) at about 40 sccm at 600 ° C, 150 sccm of TMGa, and 50,000 sccm of NH ₃ in a MOCVD system, GaN layer, and then growing the highly doped n-type GaN layer to a thickness of about 600 nm while flowing the disilane at an increased flow rate of about 60 sccm or more in the same growth environment.

As shown in the surface photograph (a), the surface of the n-type GaN window layer has innumerable curvatures and forms a fine irregular pattern. As shown in the side view (b), it can be confirmed that the concave-convex n-type GaN window layer is uniformly grown directly on the n-type AlGaInP layer. Further, as shown in the graph (c), the quantitative analysis result "N" detection indication was confirmed. Since the AlGaInP light emitting diode does not use the &quot; N &quot; material during growth, it can be judged that the material grown in high quality on the n-type AlGaInP restricted layer is GaN.

The above-described embodiments are intended to illustrate the preferred embodiments of the present invention in order to facilitate understanding of the present invention, and should not be construed as limiting the present invention. Those skilled in the art will recognize that various changes and modifications can be made within the spirit and scope of the present invention, and that the present invention is entitled to protection within the scope of the claims set forth in the claims.

Type AlGaInP active layer 5: p-type AlGaInP confinement layer 6: p-type Gap or AlGaAs window layer 7: transparent electrode 8: reflective film 9: ohmic bonding layer 5: n-type GaN window layer 4: 10: p-type Si substrate 11: lower electrode

Claims (6)

An AlGaInP-based light emitting diode having wafer bonding applied thereto or grown on a p-type substrate, wherein an n-type GaN window layer is grown on an n-type limiting layer. The AlGaInP-based light emitting diode of claim 1, wherein the n-type GaN window layer is doped with disilane (Si ₂ H ₆ ). The AlGaInP-based light emitting diode of claim 1 or 2, wherein the n-type GaN window layer has a surface characteristic of an uneven pattern. growing an n-type limiting layer, an active layer and a p-type limiting layer on an n-type substrate;
Optionally growing a p-type window layer over the p-type limiting layer;
Forming a reflective layer structure on the grown uppermost layer, bonding to a p-type substrate, and removing the n-type substrate; And
Growing an n-type GaN window layer on the n-type limiting layer;
Wherein the light emitting diode includes a first electrode and a second electrode. growing a p-type limiting layer, an active layer and an n-type limiting layer on the p-type substrate; And
Growing an n-type GaN window layer on the n-type limiting layer;
Wherein the light emitting diode includes a first electrode and a second electrode. The method of claim 4 or 5, wherein the growing of the n-type GaN window layer comprises a step of highly doping so that a concave-convex pattern is formed on the surface.

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