JP2001284650A - Semiconductor light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep the dispersion of light emission intensity at the time of forming a protective film fixed by removing an insulation film other than the one in the pull-out direction of an electrode. SOLUTION: In this semiconductor light emitting element for which a one conductivity type semiconductor layer and an opposite conductivity type semiconductor layer on a substrate and covered with the insulation film, a first electrode connected to the opposite conductivity type semiconductor layer is pulled out on the semiconductor substrate through a contact hole formed on the insulation film, the first electrode, the one conductivity type semiconductor layer and the opposite conductivity type semiconductor layer are covered with the protective film and a second electrode is connected and provided on the back surface side of the substrate, the insulation film is provided only in the pull-out direction of the first electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device, and more particularly, to a semiconductor light emitting device used for an exposure light source of a photosensitive drum for a page printer, various illumination LEDs, or an infrared LED for a remote controller or a photocoupler.

[0002]

2. Description of the Related Art An example of a conventional semiconductor light emitting device is shown in FIG. 6A is a plan view, FIG. 6B is a cross-sectional view taken along line AA ′ of FIG. 6A, and FIG. 6C is a cross-sectional view taken along line BB ′ of FIG. It is sectional drawing. 6A to 6C, 21 is a semiconductor substrate, 22 is a semiconductor layer of one conductivity type, 23 is a semiconductor layer of the opposite conductivity type, 24 is a front electrode, 25 is a back electrode, 26 is an insulating film,
27 is a protective film and 28 is a contact hole.

[0003] On a semiconductor substrate 21, a one-conductivity type semiconductor layer 2 is formed.
2 and a semiconductor layer 23 having the opposite conductivity type to the insulating film 26.
Are provided, a contact hole 28 is provided for achieving ohmic contact with the front surface electrode 24, a back surface electrode 25 is provided on the back surface side of the semiconductor substrate 21, and the front surface electrode 24 is connected to the opposite conductivity type semiconductor layer 23. . Then, a protective film 27 is formed thereon.

In such a semiconductor light emitting device, a current is caused to flow between the front electrode 24 and the back electrode 25 to cause the light emitting diode to emit light.

In such a semiconductor light emitting device, the electrode width D
₁ and a method of taking greater than the method and the contact hole width L ₁ of the electrode width D ₁ made larger than the contact hole width L _1.

The former has an electrode width D ₁ and a contact hole width L _1.
If the margin is small, misalignment may occur at the time of alignment, leading to variation in light emission. In addition, when a large margin is set for the electrode width D ₁ and the contact hole width L ₁ , the periphery of the contact hole 28 having the highest light emission intensity is covered with the surface electrode 24, which causes a problem of loss of light emission intensity. is there.

[0007] In the latter case, there is a problem that the change in the light emission intensity when the protective film 27 is formed becomes non-uniform. The reason is as follows. So that the parts and without portion of insulating film 26 on the light emitting portion is present when taking large contact hole width L ₁ than the electrode width D _1. As shown in FIG. 7, the luminous body has a luminous distribution, and the intensity distribution usually differs between wafers and between lots. Also,
The change in light emission intensity after the formation of the protective film 27 is different between the portion where the insulating film 26 is not provided and the portion where the insulating film 26 is not provided. Therefore, as a result, if the emission intensity distributions are different, the emission intensity changes will be different, which is very disadvantageous in process management.

[0008] Improving the light emission intensity of a semiconductor light emitting device has been a problem in terms of improving the performance of the semiconductor light emitting device. Regarding the emission intensity, there are some points that are sacrificed in the manufacturing method. One is the problem of light absorption in the contact layer 23c with the surface electrode 24. Usually, a semiconductor film having a small band gap is formed as the contact layer 23c in order to reduce the ohmic resistance with the surface electrode 24. However, since the band gap is small, light emitted from the light emitting layer 23a is absorbed by the contact layer 23c, leading to a decrease in light emission intensity.

Another problem is related to the shape of the luminous body. With respect to the shape of the luminous body, it is well known that the side having a reverse tapered shape reflects light at the reverse tapered portion and is taken out from the top surface of the luminous body to increase the luminous intensity. In this case, it is necessary to form a forward mesa because of the arrangement of the front surface electrode 24. For this reason, in the direction in which the surface electrode 24 is pulled out, the reflection of light emission on the side surface of the semiconductor layer cannot be used for the light emission intensity.

The present invention has been made in view of such a problem of the conventional device. By removing the insulating film in the direction other than the direction in which the electrodes are led out, the variation in the light emission intensity when the protective film is formed can be kept constant. It is an object of the present invention to provide a semiconductor light emitting device that can maintain the same.

It is another object of the present invention to provide a semiconductor light emitting device capable of removing an insulating film in a direction other than a direction in which an electrode is led out, forming an electrode, and then removing a contact layer causing light emission loss.

Further, after removing the insulating film in the direction other than the electrode lead-out direction and forming the electrode, a part of the semiconductor layer is etched to remove the forward tapered portion in the electrode lead-out direction to increase the emission intensity. It is an object of the present invention to provide a semiconductor light emitting device that enables the device.

[0013]

In order to achieve the above object, in a semiconductor light emitting device according to the first aspect, a semiconductor layer of one conductivity type and a semiconductor layer of opposite conductivity type are formed on a substrate and covered with an insulating film. Then, a first electrode connected to the opposite conductivity type semiconductor layer through a contact hole formed in the insulating film is drawn out and provided on the semiconductor substrate, and the first electrode, the one conductivity type semiconductor layer, And a semiconductor light-emitting device in which the opposite conductivity type semiconductor layer is covered with a protective film and a second electrode is connected to the back surface of the substrate.
Are provided only in the direction in which the electrodes are drawn.

In the semiconductor light emitting device according to the second aspect, a semiconductor layer having one conductivity type and a reverse conductivity type semiconductor layer having a contact layer at the uppermost portion are formed on the substrate and connected to the semiconductor layer having the opposite conductivity type. A first electrode is drawn out on the semiconductor substrate via an insulating film, and the first electrode, the one conductivity type semiconductor layer, and the opposite conductivity type semiconductor layer are covered with a protective film, and a back surface of the substrate is provided. In a semiconductor light emitting device provided with a second electrode connected to the side, the contact layer is provided only below the first electrode.

Furthermore, in the semiconductor light emitting device according to the third aspect, a semiconductor layer of one conductivity type and a semiconductor layer of opposite conductivity type are formed on a substrate, and a first electrode connected to the semiconductor layer of opposite conductivity type is formed as an insulating film. The first electrode, the one conductivity type semiconductor layer, and the opposite conductivity type semiconductor layer are covered with a protective film, and a second electrode is provided on the back surface side of the substrate. In the semiconductor light-emitting element provided by connection, the side walls of the one-conductivity-type semiconductor layer and the opposite-conductivity-type semiconductor layer opposite to the lead-out portion of the first electrode have an inverted mesa shape.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. 1A and 1B are views showing one embodiment of a semiconductor light emitting device according to the present invention, wherein FIG. 1A is a plan view, FIG. 1B is a cross-sectional view taken along the line AA ′ of FIG. a) B
It is sectional drawing of the -B 'line part.

1A to 1C, reference numeral 1 denotes a substrate;
2 is a semiconductor layer of one conductivity type, 3 is a semiconductor layer of opposite conductivity type, 4 is a first electrode, 5 is a second electrode, and 6 is an insulating film.

The substrate 1 comprises a single crystal semiconductor substrate such as silicon (Si) or a single crystal insulating substrate such as sapphire (Al ₂ O ₃ ). In the case of a single crystal semiconductor substrate, a substrate or the like in which the (100) plane is turned off by 2 to 7 ° in the <011> direction is preferably used. In the case of sapphire, a C-plane substrate is preferably used.

The one conductivity type semiconductor layer 2 includes a buffer layer 2a,
It is composed of the carrier injection layer 2b. The buffer layer 2a is 1
It is formed to a thickness of about 4 μm. The buffer layer 2a is formed of gallium arsenide or the like, and the carrier injection layer 2b is formed of aluminum gallium arsenide or the like. One conductivity type semiconductor layer 2 contains one conductivity type semiconductor impurity such as silicon at 1 × 1.
It contains about 0 ¹⁶ to 10 ¹⁹ atoms / cm ³ . Also,
At this time, the composition of Al in the carrier injection layer 2b is x = 0.2
It is formed to about 4 to 0.5. The buffer layer 2a is provided to prevent misfit dislocation due to mismatch of lattice constant between the substrate 1 and the semiconductor layer.

The opposite conductivity type semiconductor layer 3 includes a light emitting layer 3a, a cladding layer 3b, and a contact layer 3c. The light emitting layer 3a and the cladding layer 3b are formed to a thickness of about 0.2 to 0.4 μm, and the contact layer 3c is formed to a thickness of 0.01 to 0.1 μm.
It is formed to a thickness of about μm. Top contact layer 3
c is made of gallium arsenide or the like.

The light emitting layer 3a and the cladding layer 3b differ in the mixed crystal ratio between aluminum arsenide (AlAs) and gallium arsenide (GaAs) in consideration of the electron confinement effect and the light extraction effect. The light emitting layer 3a and the cladding layer 3b are made of 1 × 10 ¹⁶ to 1 × 10 ¹⁶ to 1 × 10 ¹⁶ semiconductor impurities such as zinc (Zn).
0 ¹⁸ atoms / cm ³ , and the second contact layer 3c contains 1 × 10 ^{19 of} a reverse conductivity type semiconductor impurity such as zinc.
Containing about ~10 ²⁰ atoms / cm ^3.

The insulating film 6 and the protective film 7 are made of silicon nitride or the like and have a thickness of about 3000 to 5000 °.
The first electrode 4 is made of gold / chrome (Au / Cr) or the like.
The second electrode 5 is made of a gold-antimony alloy or the like, and has a thickness of 1
It is formed to a thickness of about μm.

In this semiconductor light emitting device, as shown in FIG. 1B, the insulating film 6 is formed only in the direction in which the first electrode 4 is pulled out.
And are not formed in different directions as shown in FIG.

In the above-described semiconductor light emitting device, the first electrode 4
Light is emitted by flowing a current between the substrate and the back electrode 5.

Next, a method for manufacturing the above-described semiconductor light emitting device will be described. First, a semiconductor layer 2 of one conductivity type and a semiconductor layer 3 of opposite conductivity type are sequentially laminated on a single crystal substrate 1 by MOCVD or the like.

When these semiconductor layers 2 and 3 are formed,
First, set the substrate temperature to 400 to 500 ° C. and
After forming an amorphous gallium arsenide film to a thickness of 000 °, the substrate temperature is raised to 700 to 900 ° C. to form semiconductor layers 2 and 3 having a desired thickness.

In this case, TMG ((C
H_Three)_ThreeGa), TEG ((C_TwoH_Five) _ThreeGa), arsine
(AsH_Three), TMA ((CH_Three)_ThreeAl), TEA
((C_TwoH_Five)_ThreeAl) is used to control the conductivity type.
Silane (SiH_Four), Selenization
Hydrogen (H_TwoSe), TMZ ((CH_Three)_ThreeZn) etc.
The carrier gas is H_TwoEtc. are used
You.

Next, the semiconductor layers 2 and 3 are patterned in an island shape so that adjacent elements are electrically separated from each other. This etching is performed by wet etching using a sulfuric acid-hydrogen peroxide-based etchant, dry etching using CCl ₂ F ₂ gas, or the like. At this time, it is necessary to maintain a forward tapered shape of the electrode in order to prevent disconnection of the electrode.

Next, an insulating film 6 made of silicon nitride is formed by a plasma CVD method using silane gas (SiH ₄ ) and ammonia gas (NH ₃ ). Then, the first electrode
It is necessary to remove a part of the contact layer 3c with the electrode 4, but at this time, as shown in FIGS. 1B, 2B and 5, except for the direction in which the first electrode 4 is drawn out. The insulating film 6 is removed.

Next, a first electrode 4 and a second electrode 5 are formed by sequentially forming and patterning chromium, gold, and a gold alloy by a vapor deposition method or a sputtering method.

Finally, the protective film 7 is formed by using a method such as a plasma CVD method, a coating method, or a sol-gel method.

In the above embodiment, the use of aluminum gallium arsenide has been described. However, the present invention is not limited to this. For example, indium gallium arsenide, gallium phosphide, or the like can be used.

FIGS. 2A and 2B are views showing another embodiment of the semiconductor light emitting device according to claim 1, wherein FIG. 2A is a plan view and FIG.
3A is a cross-sectional view taken along the line AA ′ of FIG. 3A, and FIG. 3C is a cross-sectional view taken along the line BB ′ of FIG. In this embodiment, the insulating film 6 is formed only below the first electrode 4, and the insulating film 6 is not formed on the opposing side wall. Thus, even if the insulating film 6 is formed only under the first electrode 4, the same operation and effect as the above-described semiconductor light emitting device can be obtained.

FIG. 3 is a view showing one embodiment of the semiconductor light emitting device according to the second aspect. In this semiconductor light emitting device,
Before the formation of the protective film 7, the contact layer 3c is etched to improve the light emission intensity. Finally, the protective film 7 is formed by using a method such as a plasma CVD method, a coating method, or a sol-gel method.

FIG. 4 is a view showing one embodiment of the semiconductor light emitting device according to the third aspect. In this semiconductor light emitting device, before forming the protective film 7, a part of the semiconductor layer is etched to remove a forward tapered portion of the light emitting body and to form a reverse tapered shape. By doing so, the contact layer 3c is removed as described above, and the forward tapered portion becomes reversely tapered, so that the emission intensity increases. At this time, as shown in FIG. 5, when the contact hole 8 is expanded so that the insulating film 6 is formed only under the first electrode 4,
The direction in which the first electrode 4 is drawn out is even better because all the semiconductor layers other than the direction in which the first electrode 4 is drawn out are etched. Finally, the protective film 7 is formed by using a method such as a plasma CVD method, a coating method, or a sol-gel method.

[0036]

As described above, in the semiconductor light emitting device according to the first aspect, since the insulating film is provided only in the drawing direction of the first electrode, the change in the light emission intensity when the protective film is formed can be kept constant. Can be maintained.

In the semiconductor light emitting device according to the second aspect, since the contact layer is provided only under the first electrode, absorption of emitted light can be reduced as much as possible.

Furthermore, in the semiconductor light emitting device according to the third aspect, the side walls of the one conductivity type semiconductor layer and the opposite conductivity type semiconductor layer opposite to the lead-out portion of the first electrode have an inverted mesa shape. The emitted light can be reflected inside the side wall portion and extracted upward, and the efficiency of extracting emitted light can be increased.

[Brief description of the drawings]

FIGS. 1A and 1B are views showing one embodiment of a semiconductor light emitting device according to claim 1, wherein FIG. 1A is a plan view and FIG.
FIG. 3C is a cross-sectional view taken along the line A ′, and FIG. 3C is a cross-sectional view taken along the line BB ′ in FIG.

FIGS. 2A and 2B are views showing another embodiment of the semiconductor light emitting device according to claim 1, wherein FIG. 2A is a plan view and FIG.
FIG. 3C is a cross-sectional view taken along the line A-A ′, and FIG. 3C is a cross-sectional view taken along the line BB ′ in FIG.

FIG. 3 is a view showing one embodiment of a semiconductor light emitting device according to claim 2;

FIG. 4 is a view showing one embodiment of a semiconductor light emitting device according to claim 3;

FIG. 5 is a view showing another embodiment of the semiconductor light emitting device according to claim 3;

6A and 6B are views showing a conventional semiconductor light emitting device, and FIG.
Is a plan view, (b) is a cross-sectional view taken along line AA ′ of (a),
(C) is a sectional view taken along the line BB 'of (a).

FIG. 7 is a diagram illustrating an example of a light emission intensity distribution of a semiconductor light emitting element.

[Explanation of symbols]

1: substrate, 2: one conductivity type semiconductor layer, 3: reverse conductivity type semiconductor layer, 4: first electrode, 5: back electrode, 6: insulating film, 7:
Protective film, 8: contact hole

Claims (3)

[Claims] 1. A semiconductor layer of one conductivity type and a semiconductor layer of opposite conductivity type are formed on a substrate, covered with an insulating film, and connected to the semiconductor layer of opposite conductivity type via a contact hole formed in the insulating film. The first electrode, which has been drawn out on the semiconductor substrate, is provided, the first electrode, the one conductivity type semiconductor layer, and the opposite conductivity type semiconductor layer are covered with a protective film. Wherein the insulating film is provided only in the lead-out direction of the first electrode. 2. A semiconductor device comprising: a semiconductor layer having one conductivity type and a contact layer formed on the uppermost portion of the semiconductor layer; and a first electrode connected to the semiconductor layer having a conductivity type interposed therebetween through an insulating film. The first electrode, the one conductivity type semiconductor layer, and the opposite conductivity type semiconductor layer are covered with a protective film, and a second electrode is connected to the back surface side of the substrate. In the provided semiconductor light emitting device, the contact layer is provided only under the first electrode. Forming a first conductive type semiconductor layer and a reverse conductive type semiconductor layer on a substrate, drawing out a first electrode connected to the opposite conductive type semiconductor layer onto the semiconductor substrate via an insulating film; A semiconductor light-emitting element comprising: a first electrode, the one-conductivity-type semiconductor layer, and the opposite-conductivity-type semiconductor layer covered with a protective film, and a second electrode connected to the back surface of the substrate. A semiconductor light emitting device, wherein a side wall portion of the one conductivity type semiconductor layer and the opposite conductivity type semiconductor layer opposite to a lead portion of the first electrode has an inverted mesa shape.