JP2004119949A - Compound semiconductor light-emitting element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means which easily improves light-emitting output of a compound semiconductor light-emitting element. <P>SOLUTION: The compound semiconductor light-emitting element 1 is so constituted that it has a double-heterostructure, by sandwiching both sides of a light-emitting layer 2 with clad layers 3, 4 and the area of the light-emitting layer 2 is smaller than that of the clad layers 3, 4 in a state viewed from the laminating direction of the light-emitting layer 2 and the clad layers 3, 4. The compound semiconductor light-emitting element 1 is manufactured, by selectively etching the peripheral edge part of the light-emitting layer 2, after dicing. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a compound semiconductor light emitting device used for a display device, a sensor light source, and the like, and a method for manufacturing the same.
[0002]
[Prior art]
Compound semiconductor light emitting devices such as light emitting diodes and semiconductor lasers are widely used in the field of optoelectronics. Conventionally, a compound semiconductor light emitting device having a double hetero structure (DH structure) in which both sides of a light emitting layer (active layer) that emits light are sandwiched between cladding layers having a low refractive index has been known.
[0003]
FIG. 5 is an explanatory diagram of a compound semiconductor light emitting device (LED) 10 having a general double hetero structure. The compound semiconductor light emitting device 10 has a configuration in which an N-type cladding layer 12 and a P-type cladding layer 13 are stacked on and under a P-type light-emitting layer 11. In the compound semiconductor light emitting device 10, when a current is passed through the upper electrode 15 and the lower electrode (not shown), light is emitted near the interface (PN interface) between the N-type cladding layer 12 and the P-type light emitting layer 11. A phenomenon occurs. Then, the generated light is extracted outside through the N-type cladding layer 12 and the P-type cladding layer 13.
[0004]
Such a compound semiconductor light emitting device is manufactured through a film forming process and a processing process. In the film forming process, a compound semiconductor film is laminated on a single crystal substrate by an epitaxial growth technique such as an LPE (liquid phase epitaxial growth) method or an MOCVD (metal organic chemical vapor deposition) method. In the processing step, after adjusting the thickness of the epitaxial growth wafer and forming electrodes, the compound semiconductor element is obtained by processing to a desired chip size.
[0005]
The amount of light actually extracted from the compound semiconductor device to the outside (external light emission efficiency) is affected by the internal light emission efficiency at the PN interface and the external light extraction efficiency of emitted light. The internal luminous efficiency mainly depends on the epitaxial growth layer. The external extraction efficiency is affected not only by the epitaxial growth layer but also by the structure of the compound semiconductor light emitting device such as the shape of the N-type cladding layer or the P-type cladding layer that transmits light.
[0006]
It is often desired that the compound semiconductor light emitting device has a high light output, but the epitaxial film forming conditions such as the structure and composition of the epitaxial film cannot be easily changed due to the basic properties of the material and restrictions on the use of the device. There are cases. In addition, the determination of the structure of the epitaxial film usually requires a long study period. Conventionally, Japanese Unexamined Patent Publication No. Hei 6-151959 discloses a method in which fine irregularities are formed on the side surface of a compound semiconductor light emitting device and emitted light is more emitted to the outside without being absorbed by the crystal by internal reflection. I have.
[0007]
[Patent Document 1]
JP-A-6-151959 (for example, claim 1, FIG. 1)
[0008]
[Problems to be solved by the invention]
However, the method of Japanese Patent Application Laid-Open No. 6-151959 requires two different steps, namely, a step of processing a flat surface without processing distortion and a step of forming fine irregularities on the side surface, and the processing becomes complicated. .
[0009]
An object of the present invention is to provide a means for easily improving the light emission output of a compound semiconductor light emitting device.
[0010]
[Means for Solving the Problems]
In order to achieve this object, according to the present invention, there is provided a compound semiconductor light emitting device having a double hetero structure in which both sides of a light emitting layer are sandwiched by cladding layers, viewed from the laminating direction of the light emitting layer and the cladding layer. In this state, the area of the light emitting layer is smaller than the area of the cladding layer. In this case, for example, each of the light emitting layer and the cladding layer is a mixed crystal made of Al, Ga, and As, and the light emitting layer has a lower Al composition ratio than the cladding layer.
[0011]
The present invention also relates to a method of manufacturing a compound semiconductor light emitting device having a double hetero structure in which both sides of a light emitting layer are sandwiched by cladding layers, wherein after dicing, the periphery of the light emitting layer is etched. And In this case, it is preferable to use an etchant for selectively etching the light emitting layer.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. 1 and 2 are side views showing an AlGaAs light emitting device 1 as an example of a compound semiconductor light emitting device according to a manufacturing process. FIG. 1 shows a state before etching, and FIG. 2 shows an AlGaAs light emitting device 1 according to an embodiment of the present invention in an etched state. FIG. 3 is a plan view of the AlGaAs light emitting device 1 according to the embodiment of the present invention.
[0013]
First, the GaAs substrate is removed from the wafer on which AlGaAs has been epitaxially grown, electrodes and other processing are performed, and then dicing is performed to a desired chip size to obtain the AlGaAs light emitting element 1 before etching. The AlGaAs light emitting device 1 before the etching has a double hetero structure in which a P-type light emitting layer 2 is sandwiched between an N-type cladding layer 3 and a P-type cladding layer 4 from above and below. An electrode 5 is formed on the upper surface of the AlGaAs light emitting device 1 before etching (the upper surface of the N-type cladding layer 3). The N-type cladding layer 3 and the P-type cladding layer 4 have a higher Al composition ratio than the P-type light emitting layer 2 in order to increase the light transmittance. If the composition ratio of the P-type light-emitting layer 2, the N-type clad layer 3, and the P-type clad layer 4 is expressed as Al _X Ga _1-X As, for the P-type light-emitting layer 2, for example, X = 0.35, and the N-type For the cladding layer 3 and the P-type cladding layer 4, for example, X = 0.65. Further, as a dopant of each layer, for example, the P-type light emitting layer 2 and the P-type cladding layer 4 are doped with Zn, and the N-type cladding layer 3 is doped with Te.
[0014]
The AlGaAs light emitting element 1 before the etching is etched by using an etchant such as NH ₄ OH: H ₂ O ₂ : H ₂ O. Then, since the Al composition ratio of the P-type light emitting layer 2 is lower than the Al composition ratio of the N-type cladding layer 3 and the P-type cladding layer 4, the etching of the P-type light emitting layer 2 proceeds, but the Al composition ratio is high. The N-type cladding layer 3 and the P-type cladding layer 4 have a protective film of Al ₂ O ₃ formed on the surface, and the etching hardly proceeds. Thus, the P-type light emitting layer 2 is selectively etched from the peripheral portion.
[0015]
Thus, as shown in FIG. 2, the AlGaAs light emitting device 1 in which the peripheral portion of the P-type light emitting layer 2 has been removed can be obtained. In the AlGaAs light emitting device 1, as shown in FIG. 3, the P-type light emitting layer 2, the N-type cladding layer 3, and the P-type cladding layer 4 are stacked in a direction in which the peripheral portion of the P-type light emitting layer 2 is removed. When viewed from above, the area of the P-type light emitting layer 2 is smaller than the areas of the N-type cladding layer 3 and the P-type cladding layer 4.
[0016]
The etching amount of the P-type light emitting layer 2 (the removal amount of the peripheral portion of the P-type light emitting layer 2) can be easily changed by adjusting the etchant concentration and the etching time. The area ratio of the P-type light emitting layer 2, the N-type cladding layer 3, and the P-type cladding layer 4 when viewed from the laminating direction of the layer 3 and the P-type cladding layer 4 can be easily set as desired.
[0017]
When the P-type light emitting layer 2 is selectively etched as described above, the Al ₂ O ₃ film formed on the surfaces of the N-type cladding layer 3 and the P-type cladding layer 4 may come off when it becomes thick. When the peeled-off Al ₂ O ₃ accumulates around the P-type light emitting layer 2 (a gap formed between the N-type cladding layer 3 and the P-type cladding layer 4), the etchant is sufficiently supplied to the P-type light emitting layer 2. Does not penetrate into the surrounding area, and there is a fear that the progress of etching is hindered. Therefore, in order to remove the Al ₂ O ₃ film peeled off from the N-type cladding layer 3 and the P-type cladding layer 4, etching with an etchant such as HCl: H ₂ O is performed using NH ₄ OH: H ₂ O ₂ : H. _It is preferable to alternately repeat the etching with an etchant such as 2O.
[0018]
In the AlGaAs light emitting device 1 manufactured as described above, the area ratio of the N-type cladding layer 3 and the P-type cladding layer 4 to the P-type light emitting layer 2 is increased by removing the peripheral portion of the P-type light emitting layer 2. , External luminous efficiency is improved.
[0019]
The preferred embodiment of the present invention has been described above, but the present invention is not limited to the embodiment described here. For example, the present invention may be applied to a compound semiconductor light emitting device other than the AlGaAs light emitting device.
[0020]
【Example】
(Example)
An AlGaAs light emitting device having a double hetero structure from which dicing and substrate removal were performed was prepared. The composition ratio of the light emitting layer and each cladding layer is the same as that described in the embodiment. If Al _x Ga _1-x As, X = 0.35 in the P type light emitting layer and N in the N type cladding layer. X = 0.65 in the P-type cladding layer. The size of the AlGaAs light emitting device after dicing was 280 μm square and 170 μm in thickness, and the upper electrode was processed to have a diameter of 140 μm. The dicing tape on which the AlGaAs light emitting elements are aligned and adhered is expanded to widen the gap between the AlGaAs light emitting elements, and the NH ₄ OH: H ₂ O ₂ : H ₂ O = 1: 2: 100 at 30 ° C. For 4 minutes and etching for 2 minutes using an etchant of HCl: H ₂ O = 3: 100 were performed alternately. When the etching with NH ₄ OH: H ₂ O ₂ : H ₂ O and the etching with HCl: H ₂ O are performed alternately three times, two times alternately, and one time alternately Were examined individually.
[0021]
When the AlGaAs light emitting device after the etching was cleaved and the etching depth of the light emitting layer was examined, the etching with NH ₄ OH: H ₂ O ₂ : H ₂ O and the etching with HCl: H ₂ O were alternately performed three times. The etching depth when performing each of the steps was about 15 μm, the etching depth when performing each of the steps twice was about 10 μm, and the etching depth when performing each of the steps twice was about 5 μm.
[0022]
In the case where etching with NH ₄ OH: H ₂ O ₂ : H ₂ O and etching with HCl: H ₂ O were alternately performed three times, the light emitting layer was 250 μm square. The dimensions after the etching in this case are appropriately described in FIGS. In the examples shown in FIGS. 2 and 3, the area of the light emitting layer viewed from the laminating direction of the light emitting layer and each clad layer is 250 × 250 = 62,500 μm ² , and the surface area of the clad layer is incremented by upper surface + side surface + etching. = (280 × 280−70 × 70π) + (280 × 170 × 4) + (280 × 280−250 × 250) × 2 = 285,207 μm ² and the area ratio: cladding layer surface area / light emitting layer area = 4. 56. In the same manner, the area ratio is also determined when the etching with NH ₄ OH: H ₂ O ₂ : H ₂ O and the etching with HCl: H ₂ O are alternately performed twice each and once. I asked for each.
[0023]
(Comparative example)
The etching of the light emitting layer in Example 1 was omitted, and an AlGaAs light emitting device in which the peripheral portion of the light emitting layer was not removed was obtained.
[0024]
The light output of the AlGaAs light emitting device of the example was compared with the light output of the AlGaAs light emitting device of the comparative example. FIG. 4 shows the light output change rate of the AlGaAs light emitting device of each embodiment when the light output of the AlGaAs light emitting device of the comparative example without etching was set to 1 (light output of the AlGaAs light emitting device of each embodiment / comparison). 3 is a graph showing the relationship between the area ratio (cladding layer surface area / light emitting layer area) and the area ratio (cladding layer surface area / light emitting layer area) of each example. In the example in which the etching with NH ₄ OH: H ₂ O ₂ : H ₂ O and the etching with HCl: H ₂ O were alternately performed three times, a light output 1.4 times higher than that of the comparative example was obtained. .
[0025]
【The invention's effect】
According to the present invention, the light output can be improved by reducing the area of the light emitting layer and increasing the surface area ratio of the cladding layer (light transmitting layer).
[Brief description of the drawings]
FIG. 1 is a side view of an AlGaAs light emitting device before etching.
FIG. 2 is a side view of the AlGaAs light emitting device according to the embodiment of the present invention.
FIG. 3 is a plan view of the AlGaAs light emitting device according to the embodiment of the present invention.
FIG. 4 is a graph comparing the light output of the example of the present invention and the comparative example.
FIG. 5 is an explanatory diagram of a compound semiconductor light emitting device having a general double hetero structure.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 AlGaAs light emitting element 2 P type light emitting layer 3 N type clad layer 4 P type clad layer 5 Electrode

Claims (4)

A compound semiconductor light emitting device having a double hetero structure in which both sides of a light emitting layer are sandwiched by cladding layers,
A compound semiconductor light emitting device, wherein the area of the light emitting layer is smaller than the area of the cladding layer when viewed from the laminating direction of the light emitting layer and the cladding layer. The compound according to claim 1, wherein the light emitting layer and the cladding layer are all mixed crystals of Al, Ga and As, and the light emitting layer has a lower Al composition ratio than the cladding layer. Semiconductor light emitting device. A method for manufacturing a compound semiconductor light emitting device having a double hetero structure in which both sides of a light emitting layer are sandwiched by cladding layers,
A method for manufacturing a compound semiconductor light emitting device, comprising etching a peripheral portion of a light emitting layer after dicing. 4. The method according to claim 3, wherein an etchant for selectively etching the light emitting layer is used.

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