JP2003197964A - Semiconductor light emitting element and manufacturing method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that easy manufacturing of a semiconductor light emitting element having high light emitting efficiency is difficult. <P>SOLUTION: A semiconductor region 2 containing an n-type clad layer 7, an active layer 8, and a p-type clad layer 9 is provided on a substrate 1. Then a contact layer 3 and a current blocking layer 4 are provided on the semiconductor region 2, and a first electrode 5 is provided astride the layers 4 and 3. The current blocking layer 4 is formed of GaInP and all side faces of the layer 4 are formed in a normal mesa shape. <P>COPYRIGHT: (C)2003,JPO

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 such as a light emitting diode and a method for manufacturing the same.

[0002]

2. Description of the Related Art A conventional light emitting diode or LED includes a compound semiconductor substrate 1 and a light emitting semiconductor region 2 including a plurality of semiconductor layers having a light emitting function, as shown in FIGS.
A contact layer 3, a current blocking layer 4, and first and second electrodes 5 and 6. The semiconductor region 2 is composed of an n-type cladding layer 7, an active layer 8, a p-type cladding layer 9, a current spreading layer 10 and a cover layer 11. Contact layer 3 is first
It functions to achieve good ohmic contact of the electrode 5 of. The current blocking layer 4 has a conductivity type opposite to that of the contact layer 3, and is arranged at the center of the surface of the contact layer 3. Therefore, the current flowing through the central portion of the light emitting diode is suppressed by the current blocking layer 4, and the ratio of the current flowing through the peripheral portion of the light emitting diode increases. The first electrode 5 is formed so as to straddle the current block layer 4 and the contact layer 5. The first electrode 5 on the current blocking layer 4 functions as a pad for bonding a wire.

[0003]

By the way, the conventional current blocking layer 4 is formed of an AlGaInP-based compound semiconductor. An AlGaInP film having a thickness of 0.01 μm to 0.2 is formed on the contact layer 3 to obtain the current blocking layer 4.
When formed to have a thickness of about μm and selectively etched, an inverted mesa portion is formed on the side surface of the current block layer 4. That is, in the cross section taken along the line AA of FIG.
As shown in (A), the side surface of the current blocking layer 4 has an inverted mesa shape of about 60 degrees. In the cross section taken along the line BB of FIG. 1, the side surface of the current block layer 4 has a forward mesa shape of about 120 degrees as shown in FIG. 3 (B). The fact that the side surface shape of the current block layer 4 changes depending on the position is based on the difference in the crystal plane orientation indicated by the Miller index. If the first electrode 5 is formed so as to straddle the inverted mesa-shaped portion of the current blocking layer 4, the coverage of the first electrode 5 is deteriorated, and there is a possibility that a connection failure due to cracks or disconnection may occur. Even if the first electrode 5 is not broken, a gap is generated between the side surface of the current blocking layer 4 and the first electrode 5, and the reliability of the light emitting diode is reduced.

Therefore, it is an object of the present invention to provide a semiconductor light emitting device capable of preventing electrode connection failure and a method for manufacturing the same.

[0005]

SUMMARY OF THE INVENTION To solve the above problems and to achieve the above object, the present invention provides a semiconductor region including a plurality of semiconductor layers for obtaining a light emitting function, and one of the semiconductor regions. The contact layer formed on the main surface, the current block layer arranged on a part of the main surface of the contact layer, the first portion arranged on at least a part of the main surface of the current block layer, and the contact A first electrode having a second portion arranged on at least a part of the main surface of the layer and a third portion arranged so as to extend from the current block layer to the contact layer, and the other of the semiconductor regions And a second electrode electrically connected to the main surface of the current blocking layer, the current blocking layer is made of GaInP, and the entire side surface of the current blocking layer spreads toward the contact layer. It has an inclined face are those related to the semiconductor light emitting device characterized.

It is preferable that the current blocking layer has a thickness in the range of 0.03 μm to 0.08 μm. The first electrode may be made of a material having a melting point higher than that of gold, the alloy being arranged so as to contact the current blocking layer and the contact layer, and being alloyed with the contact layer. A first metal layer formed so as not to cause a reaction,
A second metal layer disposed on the first metal layer and formed of a material having a lower melting point than the first metal layer and a resistivity lower than that of the first metal layer. It is desirable to consist of Further, as described in claim 4, a step of forming a semiconductor region including a plurality of semiconductor layers for obtaining a light emitting function on the semiconductor substrate, a step of forming a contact layer on the semiconductor region, Forming a semiconductor layer made of GaInP on the main surface of the contact layer by an epitaxial growth method; selectively etching the semiconductor layer made of GaInP so that all of the side surfaces are inclined toward the contact layer in a divergent shape. Forming a trapezoidal current blocking layer, a first portion provided on at least a part of the main surface of the current blocking layer, and a second portion provided on at least a part of the main surface of the contact layer.
Forming a first electrode having a third portion arranged so as to extend from the current block layer to the contact layer, and electrically connected to the other main surface of the semiconductor region. It is desirable to manufacture the semiconductor light emitting device in the step of forming the second electrode.

[0007]

When the current blocking layer is made of a GaInP group 3-5 compound semiconductor according to the present invention, the reverse mesa portion does not occur on the side surface due to the selective etching when the current blocking layer is formed. , The entire side surface, that is, the entire circumference, has a regular mesa shape. Therefore, it is possible to prevent cracks and breaks in the third portion of the first electrode extending from the current blocking layer to the contact layer, and it is possible to provide a highly reliable semiconductor light emitting device. According to the invention of claim 2, since the current blocking layer is formed thinner than the conventional one, the coverage of the first electrode can be further enhanced. According to the invention of claim 3, even when the first electrode is formed of a material having a higher melting point than gold (Au),
It is possible to prevent cracks and breaks in the third portion of the first electrode.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to FIGS.

[0009]

First Embodiment A light emitting diode as a 3-5 group compound semiconductor light emitting device of the first embodiment shown in FIGS. 4 and 5 is roughly classified into a semiconductor substrate 1 and a light emitting semiconductor region 2.
A contact layer 3 and a current blocking layer 4a made of GaInP (gallium indium phosphide) according to the present invention.
And a first electrode 5 functioning as an anode electrode and a second electrode 6 functioning as a cathode electrode. When a forward voltage is applied between the first and second electrodes 5 and 6 of the light emitting diode, light is generated in the light emitting semiconductor region 2, and this light causes the first electrode 5 of the contact layer 3 to pass through. It is taken out from the part that does not have it. Next, each part will be described in detail.

The semiconductor substrate 1 is an n-type compound semiconductor and is made of, for example, n-type GaAs (gallium arsenide) doped with silicon (Si) as an n-type impurity. The n-type impurity concentration of this substrate 1 is about 3 × 10 ¹⁸ cm ⁻³ .

The light emitting semiconductor region 2 is arranged on one main surface of the substrate 1, and is composed of the n-type cladding layer 7, the active layer 8, the p-type cladding layer 9, the current spreading layer 10 and the cover layer 11. Become. Each of the layers 7 to 11 of the semiconductor region 2 is made of a compound semiconductor of a Group 3 element and a Group 5 element.

The n-type cladding layer 7 is arranged on one main surface of the substrate 1, and is made of, for example, In _0.5 (Ga _0.3 Al _0.7 ) _0.5 P.
It consists of the n-type compound semiconductor which can be shown by. This n
The type cladding layer 7 is doped with n-type impurities, for example, silicon (Si) at a concentration of about 4 × 10 ¹⁷ cm ⁻³ .

The active layer 8 is disposed on the n-type cladding layer 7.
For example, In_0.5(Ga_1-xAl _x)_0.5P, where x
Can be represented by a numerical value that satisfies 0 ≦ x ≦ 0.5
Composed of compound semiconductors. This active layer 8 has a conductivity type of
Impurities are not doped.

[0014] p-type cladding layer 9 is disposed on the active layer 8, for example, _{In 0.5 (Ga 0.3 Al 0. 7} ) consisting of p-type compound semiconductor may be represented by _0.5 P. In the p-type clad layer 9, for example, Zn as a p-type impurity is about 4 × 10 4.
It is doped to a concentration of ¹⁷ cm ⁻³ .

The current spreading layer 10 is disposed on the p-type cladding layer 9, and is made of, for example, Ga _1-y Al _y. As, where y
Is a p-type compound semiconductor that can be represented by a numerical value that satisfies 0 <y <1. In this embodiment, y is 0.85
Is set to. The current diffusion layer 10 is doped with p-type impurities (for example, Zn). This current spreading layer 1
0 has a well-known function of spreading the current.

The cover layer 11 is disposed on the current spreading layer 10, and is made of, for example, p-type Al _a Ga _b In _{1 -ab} P, where a,
b is a p-type compound semiconductor that can be represented by a numerical value satisfying 0 ≦ a <1 and 0 ≦ b <1. In this embodiment, a is set to 0.6 and b is set to 0.2. The cover layer 11 has a function as a buffer layer between the current diffusion layer 10 and the contact layer 3.

The contact layer 3 is a compound semiconductor layer formed on the cover layer 11 and made of, for example, p-type GaAs. P-type impurities (for example, Zn) of this contact layer 3
Is higher than those of the p-type cladding layer 9, the current spreading layer 10, and the cover layer 11, for example, 5 to 20 × 10 ¹⁸ cm ^−3.
Is.

The current block layer 4a has a circular planar shape and is arranged at the center of the surface of the contact layer 3. The current block layer 4a is an n-type compound semiconductor for blocking the forward current of the light emitting diode, and is made of, for example, n-type Ga _0.5 In _0.5 P. The ratio of Ga and In can be changed. The thickness of the current block layer 4a is preferably 0.03 to 0.08 μm. The current blocking layer 4a is formed by vapor-depositing a GaInP film on the contact layer 3 and selectively removing the GaInP film with an etching solution.
The side surface of the current block layer 4a formed by etching the GaInP film of 0.03 to 0.08 μm has a regular mesa shape over the entire circumference. That is, in the CC cross section of FIG.
As shown in FIG. 6A, the side surface of the current block layer 4a has a forward mesa shape of about 140 degrees. Further, in the cross section taken along the line DD of FIG. 4, the side surface of the current block layer 4a has a forward mesa shape of about 150 degrees as shown in FIG. 6B. In addition, the entire side surface of the current block layer 4 a becomes a sloping surface that spreads toward the contact layer 3.

The first electrode 5 is made of, for example, gold (Au) or A.
The first portion 5a made of u-Zn and arranged on the current blocking layer 4a, the second portion 5b arranged on the contact layer 3, and the current blocking layer 4a to the contact layer 3
And a third portion 5c which is arranged so as to straddle. The first portion 5a and the second portion 5b are electrically connected by the third portion 5c. The first portion 5a functions as a pad portion for bonding a wire (not shown). The second portion 5b is a strip portion arranged in a ring shape or a lattice shape on a part of the surface of the contact layer 3 and has a function of supplying a current to the contact layer 3. Since the second portion 5b is attached only to a part of the exposed portion of the contact layer 3, light can be extracted from the remaining portion of the contact layer 3.

The second electrode 6 is formed on the entire lower surface of the semiconductor substrate 1. The second electrode 6 is in resistive contact with the substrate 1.

When manufacturing the light emitting diode shown in FIG. 4 and FIG. 5, first, the semiconductor substrate 1 is prepared, for example, MO.
CVD method (Metal Organic Chemical Vapor Deposition
A GaInP film for the n-type cladding layer 7, the active layer 8, the p-type cladding layer 9, the current diffusion layer 10, the cover layer 11, the contact layer 3, and the current blocking layer 4a by a well-known epitaxial growth method such as Form sequentially. Next, the GaInP film for the current blocking layer 4a is etched with an etching solution containing, for example, hot hydrochloric acid or hot sulfuric acid to obtain the current blocking layer 4a having a predetermined pattern. Next, a metal film for the first electrode 5 is formed on the contact layer 3 and the current blocking layer 4 by a vacuum deposition method, and the metal film is etched according to the pattern of FIG. 4 to form the first electrode 5. obtain. Next, the second electrode 6 is formed by a vacuum evaporation method,
Complete the light emitting device.

In the present embodiment, the current blocking layer 4
a is made of GaInP having a thickness of 0.03 to 0.08 μm, and all of its side surfaces have a regular mesa shape. Therefore, it is possible to prevent the occurrence of cracks or disconnection in the third portion 5c of the first electrode 5 arranged so as to extend from the current block layer 4a to the contact layer 3. In addition, the current block layer 4
The coverage of the first electrode 5 with respect to the side surface of a is improved, and the reliability of the light emitting element is increased.

[0023]

Second Embodiment Next, a light emitting diode of a second embodiment will be described with reference to FIG. However, in FIG. 7 and FIGS. 8 and 9 to be described later, substantially the same parts as those in FIGS. 4 and 5 are designated by the same reference numerals, and the description thereof will be omitted.

The light emitting diode of the second embodiment of FIG. 7 is obtained by modifying the contact layer 3 and the first electrode 5 of FIG.
Other than this, the configuration is the same as that of FIG.

The modified contact layer 3a of FIG. 7 comprises first and second contact layers 12,13. The first contact layer 12 disposed directly on the cover layer 11.
Is a p-type compound semiconductor which can be represented by, for example, Al _x Ga _1-x As, where x is a numerical value smaller than 1. The first contact layer 12 of this embodiment is Al _0.4 Ga _0.6 A.
s. The concentration of the p-type impurity (for example, Zn) of the first contact layer 12 is higher than that of the p-type cladding layer 9, the current diffusion layer 10, and the cover layer 11, for example, 5 to 20 × 1.
It is 0 ¹⁸ cm ⁻³ . In addition, the first contact layer 12
The Al composition ratio is smaller than that of the current diffusion layer 10. In order to reduce light absorption, the thickness of the first contact layer 12 is preferably 0.001 to 0.05 μm, more preferably 0.001 to 0.01 μm. In this embodiment, the thickness of the first contact layer 12 is 0.01 μm. Since the first contact layer 12 acts as a buffer, it can be called a buffer layer.

The second contact layer 13 disposed on the first contact layer 12 is a compound semiconductor made of, for example, p-type GaAs. The second contact layer 13 has a p-type impurity (eg, Zn) concentration of p-type cladding layer 9,
Higher than the current spreading layer 10 and the cover layer 11, for example, 5
It is about 20 × 10 ¹⁸ cm ⁻³ . The thickness of the second contact layer 13 is 0.001 to lessen the light absorption.
Desirably in the range of 0.09 μm, 0.001
It is more desirable that the thickness is 0.01 μm. The thickness of the second contact layer 13 in this embodiment is 0.01 μm. The total thickness of the first and second contact layers 12 and 13, that is, the thickness of the contact layer 3a is 0.002 to 0.09.
It is desirable that it is μm, and 0.002-0.02 μm
Is more desirable. In the present embodiment, since the first electrode 5 does not alloy with the contact layer 3a, the contact layer 3a can be thinly formed.

The modified first electrode 5'of FIG.
And second metal layers 14, 15. The plane pattern of the first electrode 5'of FIG. 7 is the same as that of the first electrode 5 of FIG. The first metal layer 14 is made of a high melting point material that does not cause an alloying reaction with the contact layer 3a. In this embodiment, a titanium layer having a thickness of 10 nm is formed as the first metal layer 14. Titanium is a material that forms a Schottky barrier with the semiconductor. However, since the impurity concentration of the second contact layer 13 is set sufficiently high, a Schottky barrier is not formed between the first metal layer 14 made of titanium and the second contact layer 13, and the resistance contact (Ohmic contact). First metal layer 1
The second metal layer 15 disposed on the first metal layer 1
It is selected from metallic materials having a melting point lower than 4 and capable of achieving good wire connection, and in this embodiment is made of Au or gold.

When forming the first electrode 5'and the second electrode 6 of FIG. 7, the current block layer 4a and the contact layer 3 are formed.
A 10 nm-thick titanium layer for the first metal layer 14 is formed on the entire exposed surface of a by a vacuum deposition method. Next, a gold layer having a thickness of 0.5 to 1.5 μm for the second metal layer 13 is formed on the entire surface of the titanium film by a vacuum deposition method. Next, a well-known photolithography technique is used to etch the composite layer of the titanium layer and the gold layer into the same pattern as the first electrode 5 in FIG. 4 to obtain a first electrode 5 '. next,
An electrode material made of, for example, Au—Ge is vacuum-deposited on the lower surface of the substrate 1 and heat-treated at about 400 ° C. for 10 minutes to obtain the second electrode 6. The heat treatment temperature of 400 ° C. is a temperature at which the first metal layer 14 does not cause an alloying reaction with the contact layer 3a.

According to the second embodiment, the first metal layer 12 of the first electrode 5 is made of titanium and is not alloyed with the second contact layer 13. Therefore, the second contact layer 13 made of GaAs can be made extremely thin, 0.01 μm. As a result, for example, the light absorptivity of the pure green second contact layer 13 having a wavelength of 560 nm can be suppressed to about 6%. Conventional 0.1 μm GaAs
Since the light absorption rate of the contact layer is about 50%, the structure of the present embodiment can significantly reduce the light absorption in the contact layer 3a and enhance the light extraction efficiency of the light emitting diode. The second embodiment also has the same effect as the first embodiment.

[0030]

[Third Embodiment] A light emitting diode of a third embodiment shown in FIG. 8 is obtained by modifying the contact layer 3a of the light emitting diode of the second embodiment of FIG. 7 and adding a light reflecting layer 20. Others are the same as those in FIG. 7. The modified contact layer 3b of FIG. 8 has first and second contact layers 12 and 13 as in FIG. 7, but only these patterns are different from FIG. That is, the contact layer 3b of FIG. 8 exists only under the second portion 5b of the first electrode 5 and the current block layer 4, and the other portions are removed by etching.

Although lateral etching also occurs when the contact layer 3b is wet-etched, the lateral etching does not pose a problem because the contact layer 3b is extremely thin.

The light reflecting layer 20 of FIG. 8 is made of a compound semiconductor having a light reflecting property, which is arranged between the substrate 1 and the n-type cladding layer 7. The light reflection layer 20 is, for example, n-type GaA.
The s layer and the n-type In _0.5 A _0.5 P layer are alternately laminated a plurality of times (for example, 10 times), and the light emitted from the light emitting semiconductor region 2 to the second electrode 6 is applied to the first electrode. It has the function of reflecting to the 5 side.

According to the light emitting diode of the third embodiment, in addition to the same effect as that of the first embodiment, the light extraction efficiency is improved by removing a part of the contact layer 3b, and the light reflecting layer 20. Therefore, the light extraction efficiency can be improved.

[0034]

[Fourth Embodiment] A light emitting diode of a fourth embodiment shown in FIG. 9 is the same as that of FIG. 5 except that the first electrode 5 of FIG. 5 is modified.

The first electrode 5 "in FIG. 9 comprises a well-known transparent electrode 14a and a pad electrode 15a. Transparent electrode 14a
Are arranged so as to cover the entire exposed surfaces of the current blocking layer 4a and the contact layer 3 according to the present invention. Therefore, the transparent electrode 14 a is the first portion 5 a that covers the current blocking layer 4.
And a second portion 5b covering the contact layer 3 and a third portion 5c extending from the current block layer 4 to the contact layer 3. The pad electrode 15a is arranged on the current block layer 4a via the transparent electrode 14a.

Also in the embodiment of FIG. 9, the transparent electrode 14a
It is possible to prevent cracking or cutting of the third portion 5c of the same as in the case of the first electrode 5 of FIG.

[0037]

[Modification] The present invention is not limited to the above-described embodiment, and the following modifications are possible. (1) The compound semiconductor material of the substrate 1, the semiconductor region 2, and the contact layer 3 can be a group 3-5 compound semiconductor other than those described in the embodiments. (2) The first contact layer 12 can be omitted. (3) The pattern of the second portion 5b can be variously modified into a lattice shape or a net shape. (4) A plurality of layers forming the semiconductor region 2 can be increased or decreased. (5) In FIGS. 5, 7, and 9, a buffer layer made of a compound semiconductor can be interposed between the substrate 1 and the n-type cladding layer 7. Further, a buffer layer may be interposed between the substrate 1 and the light reflection layer 20 of FIG.

[Brief description of drawings]

FIG. 1 is a plan view showing a conventional light emitting diode.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a cross-sectional view showing a part of line AA and line BB in FIG. 1 in an enlarged manner.

FIG. 4 is a plan view showing a light emitting diode according to a first embodiment of the present invention.

5 is a cross-sectional view taken along line CC of FIG.

6 is an enlarged cross-sectional view showing a part of line CC and line DD of FIG.

FIG. 7 is a cross-sectional view showing a light emitting diode of a second embodiment.

FIG. 8 is a sectional view showing a light emitting diode of a third embodiment.

FIG. 9 is a cross-sectional view showing a light emitting diode of a fourth embodiment.

[Explanation of symbols]

1 substrate 2 Semiconductor region for light emission 3 Contact layer 4a GaInP current blocking layer 5 First electrode 6 Second electrode

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Claims (4)

[Claims] 1. A semiconductor region including a plurality of semiconductor layers for obtaining a light emitting function, a contact layer formed on one main surface of the semiconductor region, and a part of the main surface of the contact layer. Current blocking layer, a first portion arranged on at least a part of the main surface of the current blocking layer, a second portion arranged on at least a part of the main surface of the contact layer, and the current blocking layer To a contact layer, a first electrode having a third portion arranged so as to extend over the contact layer, and a second electrode electrically connected to the other main surface of the semiconductor region. 2. The semiconductor light emitting device according to claim 1, wherein the current block layer is made of GaInP, and all of the side surfaces of the current block layer have an inclined surface that spreads toward the contact layer. 2. The semiconductor light emitting device according to claim 1, wherein the current blocking layer has a thickness in the range of 0.03 μm to 0.08 μm. 3. The first electrode is made of a material arranged to contact the current blocking layer and the contact layer and having a melting point higher than that of gold, and does not cause an alloying reaction with the contact layer. A first metal layer formed as described above, and the first metal layer disposed on the first metal layer and the first metal layer.
3. The second metal layer formed of a material having a lower melting point than that of the first metal layer and a resistivity lower than that of the first metal layer. Semiconductor light emitting device. 4. A step of forming a semiconductor region including a plurality of semiconductor layers for obtaining a light emitting function on a semiconductor substrate, a step of forming a contact layer on the semiconductor region, and a main part of the contact layer. A step of forming a GaInP semiconductor layer on the surface by an epitaxial growth method; and a trapezoidal shape in which the GaInP semiconductor layer is selectively etched so that all of the side surfaces incline toward the contact layer toward the end. Forming a current blocking layer, a first portion arranged on at least a part of the main surface of the current blocking layer, a second portion arranged on at least a part of the main surface of the contact layer, and the current A step of forming a first electrode having a third portion arranged so as to extend from the block layer to the contact layer, and an electric field is formed on the other main surface of the semiconductor region. The connected to 2
And a step of forming an electrode, the method for manufacturing a semiconductor light emitting device.