JP2001111106A - Gallium nitride compound semiconductor light emitting device and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gallium nitride compound semiconductor light emitting device capable of emitting lights in a blue light range which solves the problems such as the forward voltage increase or nonuniform current injection due to the breakage or resistance increase of electrodes on the substrate side faces about electrodes formed from the substrate. SOLUTION: The gallium nitride compound semiconductor light emitting device having an n-type gallium nitride compound semiconductor layer 2, a light emitting layer 3 and a p-type gallium nitride compound semiconductor layer 4 formed on a substrate 1 comprises a layer 2a containing an n-type impurity at a high concentration formed between the substrate 1 and the n-type gallium nitride compound semiconductor layer, a part of the substrate backside opposite to the semiconductor laminate surface is removed down to a depth at least to the layer 2a containing the n-type impurity at the high concentration, and an ohmic metal film 6 is formed on the substrate backside and a layer 2a containing a first conductivity type impurity at a high concentration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gallium nitride-based compound semiconductor light emitting device capable of emitting light in the blue region and a method of manufacturing the same, and more particularly, to a gallium nitride based compound semiconductor light-emitting device having an electrode formed from the substrate side and its manufacture. About the method.

[0002]

2. Description of the Related Art FIG. 12 is a sectional view of a conventional gallium nitride compound semiconductor light emitting device.

An N-type gallium nitride-based compound semiconductor layer 200, a P-type gallium nitride-based compound semiconductor layer 300, and an electrode 400 for a P-type layer are sequentially formed on an insulating sapphire substrate 100. On the exposed surface of the compound semiconductor layer 200, an N-type pad electrode 500 and on a surface of the P-type layer electrode 400, a P-type pad electrode 600 are diagonally arranged on the same plane. Such a conventional gallium nitride-based compound semiconductor light emitting device is disclosed in, for example, JP-A-6-338.
632.

FIG. 13 shows a cross-sectional structural view of another conventional gallium nitride-based compound semiconductor light emitting device.

On an insulating sapphire substrate 110, an N-type gallium nitride-based compound semiconductor layer 210, a gallium nitride-based compound semiconductor active layer 710, and a P-type gallium nitride-based compound semiconductor layer 310 are sequentially formed. After a P-type pad electrode 610 is formed on the surface of the gallium-based compound semiconductor layer 310 and an insulator layer 810 for preventing a short circuit on the side surface of the compound semiconductor layer is formed, the pad electrode 610 is formed on the back surface and the side surface of the sapphire substrate 110. An N-type electrode 510 is formed on the side surface of the N-type gallium nitride-based compound semiconductor layer 210 and on the insulator layer 810. Such another conventional gallium nitride-based compound semiconductor light emitting device is disclosed in, for example,
No. 102549.

FIGS. 14A and 14B are cross-sectional structural views of another conventional gallium nitride-based compound semiconductor light emitting device.

On an insulating sapphire substrate 120, an N-type gallium nitride-based compound semiconductor layer 220, a P-type gallium nitride-based compound semiconductor layer 320, and a P-type layer electrode 420 are sequentially formed. From
After removing a part of the sapphire substrate 120 to a depth reaching the N-type gallium nitride-based compound semiconductor layer 220, an N-type layer electrode 520 is formed on the exposed surface of the N-type gallium nitride-based compound semiconductor layer 220. Such another conventional gallium nitride-based compound semiconductor light emitting device is disclosed in, for example, Japanese Patent Application Laid-Open No. 7-221347.

[0008]

However, the gallium nitride-based compound semiconductor light emitting device according to the above prior art has the following problems.

That is, in the conventional gallium nitride-based compound semiconductor light emitting device shown in FIG. 12, an N-type pad electrode 500 is provided on the surface of the N-type gallium nitride-based compound semiconductor layer 200 and the P-type layer electrode 400. And P-type pad electrode 60
One of the features is that 0 is diagonally arranged on the same plane.

In such a conventional gallium nitride-based compound semiconductor light-emitting device, an Au wire including an Au ball is ultrasonically thermocompression-bonded to these pad electrodes 500 and 600 in order to make an electrical connection with the outside. Is common.
Here, the Au wire or each semiconductor layer and the pad electrode 50
Considering the adhesive strength to 0,600, etc., the size of each pad electrode 500,600 needs to be a circular or square shape with a diameter of 100 μm to 150 μm.

Since the N-type pad electrode 500 and the P-type pad electrode 600 are formed on the same surface, GaAs
When a chip having the same size as a semiconductor light emitting device such as a GaP-based, InP-based, or the like is formed, most of the upper surface of the chip is occupied by these pad electrodes 500 and 600, and the efficiency of extracting light emitted from the upper surface of the chip to the outside. And the pad electrodes 500 and 600 are arranged close to each other to reduce Au in the wire bonding process.
Short-circuit failure due to contact of a ball or Au wire, or chip appearance or chip cracking when hitting an Au wire at the end of the chip may cause problems such as deterioration of characteristics, decrease in reliability, and decrease in yield. Was. On the other hand, if the area per chip is increased for the purpose of preventing the above problems, the number of chips that can be obtained from one wafer is limited, and the production time and material cost increase in order to produce the same quantity. Therefore, there is a problem that the unit price of the final product is increased.

Further, in another conventional gallium nitride-based compound semiconductor light emitting device shown in FIG. 13, on the back surface and the side surface of the sapphire substrate 110, on the side surface of the N-type gallium nitride-based compound semiconductor layer 210, and on the insulator layer 910. One of the features is that an N-type electrode 510 is formed at this time and is electrically connected to the N-type gallium nitride-based compound semiconductor layer 210.

In such a conventional gallium nitride-based compound semiconductor light emitting device, the thickness of the sapphire substrate 110 must be 100 μm or more even after polishing in order to maintain the mechanical strength of the device.
About 200 μm is required. On the other hand, the N-type electrode 510
Is about 0.2 to 0.3 μm at most, and the film thickness of the N-type electrode 510 is different from that of the sapphire substrate 110 by about three digits. For this reason, the N-type electrode 510 is formed on the back surface and the side surface of the sapphire substrate 110, and is electrically connected to the side surface of the N-type gallium nitride-based compound semiconductor layer 210. Disconnection or partial thinning of the N-type electrode 510 occurs, and the resistance of the N-type electrode 510 increases, and the forward voltage increases and the current to be supplied from the N-type electrode 510 becomes N-type nitrided. There is a problem that the gallium-based compound semiconductor layer 210 is not sufficiently supplied.

In another conventional gallium nitride compound semiconductor light emitting device shown in FIG. 14, after removing a part of the sapphire substrate 120 to a depth reaching the N-type gallium nitride compound semiconductor layer 220, One of the features is that an N-type layer electrode 520 is formed on the exposed surface of the N-type gallium nitride-based compound semiconductor layer 220.

In such a conventional gallium nitride-based compound semiconductor light emitting device, the thickness of the sapphire substrate 110 must be 100 μm or more even after polishing in order to maintain the mechanical strength of the device.
A thickness of about 200 μm is necessary. For example, when mounting an element on a lead frame or a mounting board, a gap is generated between the N-type layer electrode 520 and the lead frame or the mounting board, which results in poor electrical connection with the outside. However, there are problems such as deterioration of characteristics, deterioration of reliability, and decrease of yield. In order to prevent this, it is necessary to devise a method such as forming a part of the shape of the lead frame or the mounting substrate to be convex, which causes a problem that the manufacturing cost is increased.

The P-type layer electrode 420 and the N-type layer electrode 5
The electrode 20 has a thickness of several μm in order to sufficiently connect to the outside, and the P-type layer electrode 420 and the N-type layer electrode 520 are opaque layers that do not transmit light. Therefore, light is emitted from the N-type gallium nitride-based compound semiconductor layer 220 to the P-type
Is emitted to the outside only from the side surfaces of the n-type gallium nitride-based compound semiconductor layer 320 and from the interface between the n-type gallium nitride-based compound semiconductor layer 220 and the sapphire substrate 120, thereby reducing the light extraction efficiency. There was a point.

The P-type layer electrode 420 and the N-type layer electrode 5
20 is not ohmic, so it is difficult to obtain good ohmic properties with the compound semiconductor layer,
Since the current flows intensively right above the N-type layer electrode 520, the luminous efficiency is reduced. Further, the luminous efficiency of the portion immediately above the sapphire substrate 120 from which light can be extracted to the outside is particularly reduced. There has been a problem that the light extraction efficiency itself decreases.

[0018]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has at least a first conductivity type gallium nitride based compound semiconductor layer formed on a substrate, a light emitting layer, and a second conductivity type gallium nitride. In a gallium nitride-based compound semiconductor light emitting device having a laminated structure having a base compound semiconductor layer, a layer containing a high concentration of a first conductivity type impurity is formed between a substrate and a first conductivity type gallium nitride-based compound semiconductor layer. ,
A portion of the back surface of the substrate opposite to the surface on which the laminated structure is formed is removed at least to a depth that reaches a layer containing a high-concentration first-conductivity-type impurity. The above object is achieved by forming an ohmic electrode on a layer containing a type impurity.

According to the above configuration, one of the pad electrodes, which had conventionally been required to be formed on the same surface, can be formed on the back surface of the substrate. It is possible to prevent the appearance defect and the like that have been caused. Further, since the area of the light emitting element chip can be reduced, the number of chips that can be obtained from one wafer can be increased. Furthermore,
By forming a layer containing a high concentration of the first conductivity type impurity, the current is spread on the first conductivity type gallium nitride-based compound semiconductor layer side, and good ohmic connection is achieved by forming an ohmic electrode. Is obtained, and the luminous efficiency can be improved. Incidentally, the expression `` ohmic '' described in the present invention means that a good ohmic connection with the semiconductor layer is possible, for example, even when formed on an insulating substrate such as a sapphire substrate, If the same material is used, the same expression is used for convenience even if the formation is not continuous from above the semiconductor layer.

The above object is achieved by forming the ohmic electrode continuously also on the step side surface between the back surface of the substrate and the layer containing a high concentration of the first conductivity type impurity.

According to the above configuration, the entire back surface of the substrate can be used for electrical connection with the outside, so that poor electrical connection to the outside due to a gap between the lead frame for mounting the light emitting element chip and the mounting substrate is eliminated. Does not occur. Further, it is not necessary to perform special processing on the lead frame or the mounting board, and the conventional lead frame or mounting board can be used as it is.

A layer containing a high-concentration first conductivity type impurity is formed between the substrate and the first conductivity type gallium nitride compound semiconductor layer, and a layer on the back surface of the substrate opposite to the surface on which the laminated structure is formed is formed. The portion is removed at least to a depth reaching the first conductivity type gallium nitride compound semiconductor layer, and on the back surface of the substrate and on the back surface of the first conductivity type gallium nitride compound semiconductor layer and the second conductivity type gallium nitride compound semiconductor. The above object is achieved by forming an ohmic electrode on the layer. The ohmic metal electrode is formed on the ohmic metal electrode and on the first conductivity type gallium nitride-based compound semiconductor layer, and on the side surface between the back surface of the substrate and the layer containing a high concentration of the first conductivity type impurity. The above object is achieved by being formed continuously.

According to the above construction, the spread of the current on both sides of the gallium nitride compound semiconductor layer of the first conductivity type and the gallium nitride compound semiconductor layer of the second conductivity type is ensured. Since the current is diffused evenly, uniform light emission is performed as a whole, and the luminous efficiency can be improved. Also, since the entire back surface of the substrate can be used for electrical connection with the outside, there is no electrical connection failure with the outside due to gaps between the light emitting element chip mounting lead frame and the mounting substrate. Further, it is not necessary to perform special processing on the lead frame or the mounting board, and the conventional lead frame or mounting board can be used as it is.

The above object is achieved by forming the ohmic electrode with a multilayer structure of an ohmic metal electrode and a light-transmitting oxide semiconductor layer.

According to the above structure, even if the ohmic electrode is disconnected or partially thinned on the back and side surfaces of the substrate, the forward voltage can be increased by forming the oxide semiconductor layer. In addition to the above, stable current supply becomes possible. Further, a preferable mode in this case is to form a metal on the side in contact with the substrate and to form a light-transmitting oxide semiconductor thereon, and to form an ohmic electrode by using an N-type gallium nitride-based compound semiconductor layer and an ohmic electrode. The oxide semiconductor layer is formed so as to cover the disconnection of the ohmic electrode on the back surface and the side surface of the substrate and the partially thinned portion, so that the current can be smoothly applied to the N-type gallium nitride-based compound semiconductor layer. The current can be supplied to the light emitting element chip without any trouble.

The ohmic metal electrode is formed at least on the back surface of the substrate and on a layer containing a high concentration of the first conductivity type impurity. The oxide semiconductor layer is formed on the ohmic metal electrode and the back surface of the substrate. The above object is attained by being continuously formed on the step side surface between the upper portion and a layer containing a high concentration of the first conductivity type impurity. The ohmic metal electrode is formed at least on the back surface of the substrate and on the first conductivity type gallium nitride compound semiconductor layer, and the oxide semiconductor layer is formed on the ohmic metal electrode and the first conductivity type gallium nitride compound semiconductor. The above object is achieved by being formed on the layer and also continuously formed on the side surface of the back surface of the substrate and the side surface of the layer containing a high concentration of the first conductivity type impurity.

According to the above configuration, the entire back surface of the substrate can be used for electrical connection to the outside, so that poor electrical connection to the outside due to a gap between the lead frame for mounting the light emitting element chip and the mounting substrate. Does not occur. Further, it is not necessary to perform special processing on the lead frame or the mounting board, and the conventional lead frame or mounting board can be used as it is. Further, since the oxide semiconductor layer has a light-transmitting property, light to the back surface and the side surface of the substrate is exposed to a portion where the ohmic metal electrode is not formed, for example, the side surface of the substrate and a broken portion or a partially thinned portion of the ohmic electrode. Since the light is emitted to the outside from the light source and the like, the efficiency of extracting light to the outside can be improved.

The above object is achieved by forming the ohmic metal electrode from a translucent ohmic metal thin film.

According to the above configuration, since the light from the light emitting layer is not blocked by the electrode pad, it is possible to efficiently radiate the light to the outside.

In the method of manufacturing a gallium nitride-based compound semiconductor light-emitting device according to the present invention, at least a first conductivity type gallium nitride-based compound semiconductor layer, a light-emitting layer, and a second conductivity-type gallium nitride-based compound semiconductor layer formed on a substrate are provided. In the method for manufacturing a gallium nitride-based compound semiconductor light emitting device composed of a laminated structure having a step of forming a layer containing a high concentration of the first conductivity-type impurity in a part of the first conductivity-type gallium nitride-based compound semiconductor layer, A step of forming a layer containing a high concentration of the first conductivity type impurity on a part of the first conductivity type gallium nitride based compound semiconductor layer, and a part of the back surface of the substrate opposite to the surface on which the laminated structure is formed, A step of removing at least to a depth reaching a layer containing a high concentration of the first conductivity type impurity, and a step of forming an ohmic electrode on the back surface of the substrate and on the layer containing a high concentration of the first conductivity type impurity To achieve the above object by.

According to the above-described manufacturing method, the step of removing the second conductivity type gallium nitride-based compound semiconductor layer for forming the electrode, which is conventionally required, is not required, so that the entire surface of the formed light emitting element is used as the light emitting layer. It becomes possible to use it, and it becomes possible to prevent interface deterioration of the light emitting layer portion in the removing step. Further, since the ohmic electrode is formed on the back surface of the substrate and on the entire surface of the layer containing the high-concentration first conductivity type impurity, the spread of current on the first conductivity type gallium nitride-based compound semiconductor layer side is ensured, and the ohmic electrode is formed. By forming the conductive electrode, good ohmic connection can be obtained, and uniform light emission and improvement in light emission efficiency can be achieved.

[0032]

Embodiments of the present invention will be described in detail below. In the embodiments of the present invention described below, a gallium nitride-based compound semiconductor is, for example, In
_{x Al y Ga 1- xy N (} 0 ≦ x, 0 ≦ y, x + y ≦ 1) is intended to include.

<First Embodiment> A gallium nitride-based compound semiconductor light emitting device according to a first embodiment of the present invention will be described with reference to FIG.

FIG. 1 is a sectional structural view of a gallium nitride-based compound semiconductor light emitting device manufactured by using the first embodiment of the present invention.

As shown in FIG. 1, an N-type gallium nitride-based compound semiconductor layer 2, a gallium nitride-based compound semiconductor light-emitting layer 3, and a P-type gallium nitride-based compound semiconductor layer 4 are sequentially laminated on a sapphire substrate 1, for example. A laminated structure is formed. Here, for example, Si, Ge, Sn, S, S is provided between the substrate 1 and the N-type gallium nitride-based compound semiconductor layer 2.
A group IV or group VI N-type impurity such as e or Te is added to 1 × 10 ¹⁷
An N-type gallium nitride-based compound semiconductor layer 2a doped at a high concentration of about 1 × 10 ²¹ cm ⁻³ is formed. The light emitting layer includes a single quantum well and a multiple quantum well light emitting layer. In the present invention, a conductive substrate such as GaN or SiC can be used.
The present invention is most effective when used for a light-transmitting substrate.

On the P-type gallium nitride-based compound semiconductor layer 4, a pad electrode 5 for making an electrical connection with the outside such as a lead frame or a circuit wiring board is formed. The pad electrode 5 is made of, for example, Au, Au alloy, Al
The thickness is set to 0.5 μm or more and 0.8 μm or less in order to prevent electrode peeling during bonding. Note that a P-type gallium nitride-based compound semiconductor contact layer may be formed between the pad electrode 5 and the P-type gallium nitride-based compound semiconductor layer 4 in order to obtain good conductivity.

On the back and side surfaces of the substrate 1 and on the N-type gallium nitride-based compound semiconductor layer 2a heavily doped with N-type impurities, a translucent ohmic metal thin film 6 and a translucent oxidized Object semiconductor layers 7 are sequentially formed. For example, Au, Ni, T
i, Pt, Pd, and the like are formed using a vacuum evaporation method, an electron beam evaporation method, or the like. The oxide semiconductor layer 7 is made of In ₂ O ₃ , S
It is formed of one of nO ₂ , ZnO, Cd ₂ SnO ₄ , and CdSnO ₃ , and is formed by a vapor deposition method, a sputter method, a CVD method, or the like. Note that the thickness of the oxide semiconductor layer 7 is preferably in the range of 5 μm to 15 μm in consideration of securing the thickness on the side surface of the substrate and the light transmittance of 40% or more.
Further, even if In ₂ O ₃ to which Ti is added is used as the oxide semiconductor layer 7, Ti may be added because the film resistance and the transmittance do not deteriorate.

For the electrical connection between the pad electrode 5 and the outside,
For example, a metal wire 8 of Au, Al, Cu or the like is used. On the other hand, the ohmic metal thin film 6 and the oxide semiconductor layer 7
For electrical connection between the device and the outside, for example, solder, Ag paste, conductive adhesive, or the like is used.

As described above, the back surface and the side surface of the substrate 1 where the electrode has a high resistance due to the disconnection or thinning of the electrode and the N-type gallium nitride-based compound semiconductor layer 2a doped with the N-type impurity at a high concentration By sequentially forming the ohmic metal thin film 6 and the oxide semiconductor layer 7 on the top, a light-emitting element having no problem in electrical characteristics can be obtained, the efficiency of extracting light outside increases, and the light emission from one wafer can be improved. Therefore, a gallium nitride-based compound semiconductor light emitting device excellent in mass productivity can be provided.

The gallium nitride-based compound semiconductor light-emitting device having the above structure has been described with reference to a homostructure light-emitting device. However, a gallium nitride-based compound semiconductor light-emitting device may have a double hetero structure, a single hetero structure, or an active layer. Needless to say, the present invention can be applied to any structure such as a quantum well structure.

It is also possible to form a single ohmic metal electrode on the back and side surfaces of the substrate 1 and on the N-type gallium nitride-based compound semiconductor layer 2a heavily doped with N-type impurities. . In this case, although the light extraction efficiency in the direction of the back surface of the substrate is limited, a sufficient ohmic connection can be obtained between the semiconductor layer and the electrode, so that a light-emitting element having no problem in electrical characteristics can be obtained, and a single wafer can be used. Therefore, a gallium nitride-based compound semiconductor light emitting device excellent in mass productivity can be provided.

Next, a specific method of manufacturing the gallium nitride-based compound semiconductor light emitting device according to the first embodiment will be described in detail.

FIGS. 2A to 2C are process diagrams showing a method for manufacturing a gallium nitride-based compound semiconductor light emitting device using the first embodiment of the present invention.

As shown in FIG. 2A, the sapphire substrate 1
A stacked structure in which an N-type gallium nitride-based compound semiconductor layer 2, a gallium nitride-based compound semiconductor light-emitting layer 3, and a P-type gallium nitride-based compound semiconductor layer 4 are sequentially stacked is formed thereon.
Here, the substrate 1 and the N-type gallium nitride-based compound semiconductor layer 2
Between them, an N-type gallium nitride-based compound semiconductor layer 2a doped with an N-type impurity at a high concentration is formed. Next, P
Au having a thickness of 0.5 as a pad electrode 5 for making electrical connection with the outside on the p-type gallium nitride-based compound semiconductor layer 4
μm is formed.

Next, as shown in FIG. 2B, after the substrate 1 is polished to a thickness of about 100 μm, separation grooves 9 are formed on the back surface of the substrate 1 by, for example, wet etching, dry etching, dicing, It is formed by scribing or the like. Further, a second separation groove (not shown) is also formed in a direction perpendicular to the separation groove 9. The formation of the separation groove 9 and the second separation groove is performed until the N-type gallium nitride-based compound semiconductor layer 2a doped with the N-type impurity at a high concentration is exposed.

Next, as shown in FIG. 2C, the back surface and side surfaces of the substrate 1 and the N-type gallium nitride-based compound semiconductor layer 2a doped with an N-type impurity at a high concentration have translucency. 7 nm of Ni is formed as the ohmic metal thin film 6.
Next, a translucent oxide semiconductor layer 7 made of In ₂ O ₃ using Sn as a dopant is formed to a thickness of 5 μm on the ohmic metal thin film 6.

The gallium nitride-based compound semiconductor light emitting device manufactured by the above manufacturing method is scribed into a chip by scribing 250 μm square from the growth surface side.

As described above, when the back electrode of the substrate has the back electrode structure of the present invention, the metal electrode does not break or become thinner on the side surface of the substrate, and the electrode does not have a high resistance. A gallium nitride-based compound semiconductor light emitting device that can reduce the voltage and easily supply an external current to the chip, and can form one electrode on the back surface of the substrate to reduce the chip area, and is inexpensive and excellent in mass productivity Can be produced.

<Second Embodiment> A gallium nitride-based compound semiconductor light emitting device according to a second embodiment of the present invention will be described with reference to FIG.

FIG. 3 is a cross-sectional structural view of a gallium nitride-based compound semiconductor light emitting device manufactured by using the second embodiment of the present invention.

As shown in FIG. 3, an N-type gallium nitride-based compound semiconductor layer 22, a gallium nitride-based compound semiconductor light-emitting layer 23, and a P-type gallium nitride-based compound semiconductor layer 24 are sequentially laminated on a sapphire substrate 21, for example. A laminated structure is formed. Here, between the substrate 21 and the N-type gallium nitride-based compound semiconductor layer 22, for example, Si, Ge, Sn,
A group IV or group VI N-type impurity such as S, Se, Te, etc.
An N-type gallium nitride-based compound semiconductor layer 22a doped at a high concentration of 10 ¹⁷ to 1 × 10 ²¹ cm ⁻³ is formed.
The light emitting layer includes a single quantum well and a multiple quantum well light emitting layer. Although the present invention can use a conductive substrate such as GaN or SiC, the present invention is most effective when used for an insulating or translucent substrate such as the sapphire substrate 21.

On the P-type gallium nitride-based compound semiconductor layer 24, an ohmic electrode 25a and a pad electrode 25 for making electrical connection with the outside such as a lead frame or a circuit wiring board are formed. The ohmic electrode 25a is made of, for example, Au, Ni, Ti, Pt, Pd, or the like by a vacuum evaporation method,
It is formed using an electron beam evaporation method or the like. Ohmic electrode 2
The thickness of 5a varies depending on the purpose of use, but is from 1 nm to several μm.
Form between The pad electrode 25 is made of, for example, Au, Au
It is made of an alloy, Al, or the like, and has a thickness of 0.5 μm or more to prevent electrode peeling during bonding.
It is formed to a thickness of 8 μm or less.

The rear surface and the side surface of the substrate 21, the side surface of the N-type gallium nitride-based compound semiconductor layer 22a doped with an N-type impurity at a high concentration, and the surface of the N-type gallium nitride-based compound semiconductor layer 22 An ohmic metal thin film 26 having the following characteristics and an oxide semiconductor layer 27 having a light-transmitting property are sequentially formed. For example, Au, N
i, Pt, Pd, and the like are formed using a vacuum evaporation method, an electron beam evaporation method, or the like. The oxide semiconductor layer 27 is made of In ₂ O ₃ ,
It is made of one of SnO ₂ , ZnO, Cd ₂ SnO ₄ , and CdSnO ₃ and is formed by using an evaporation method, a sputter method, a CVD method, or the like. Note that the thickness of the oxide semiconductor layer 27 is preferably in the range of 5 μm to 15 μm in consideration of securing the film thickness on the side surface of the substrate and light transmittance of 40% or more. In addition, as the oxide semiconductor layer 27, In
_{Even if 2} O ₃ is used, Ti may be added because the film resistance and transmittance do not deteriorate.

For electrical connection between the pad electrode 25 and the outside, a metal wire 28 of, for example, Au, Al, Cu or the like is used. On the other hand, for electrical connection between the ohmic metal thin film 26 and the oxide semiconductor layer 27 and the outside, for example, solder, A
g paste, conductive adhesive or the like is used.

As described above, by forming the ohmic electrode 25a on the P-type gallium nitride based compound semiconductor layer 24, the spread of current on the P side can be ensured.
Since the current spreads and flows through the entire light emitting layer 23, the light emission efficiency is improved. In this embodiment, the N-type gallium nitride-based compound semiconductor layer 22a doped with the N-type impurity at a high concentration is formed only on the upper surface of the substrate 21. As a result, the current is uniformly diffused even on the portion of the substrate surface where the current does not easily flow, so that uniform light emission is performed as a whole and the light emission efficiency can be improved.

Further, the back surface and side surface of the substrate 21 in which the electrode has a high resistance due to the disconnection and thinning of the electrode, and the side surface of the N-type gallium nitride-based compound semiconductor layer 22a doped with an N-type impurity at a high concentration. , N-type gallium nitride-based compound semiconductor layer 2
Ohmic metal thin film 26, oxide semiconductor layer 2
By sequentially forming 7, a light-emitting element having no problem in electrical characteristics can be obtained, the efficiency of extracting light outside increases, and the number of chips taken from one wafer increases, resulting in excellent mass productivity. Gallium nitride based compound semiconductor light emitting device.

The gallium nitride-based compound semiconductor light-emitting device having the above-described structure has been described with reference to a homostructure light-emitting device. Needless to say, the present invention can be applied to any structure such as a quantum well structure.

Also, the back surface and side surfaces of the substrate 21, the side surfaces of the N-type gallium nitride-based compound semiconductor layer 22a heavily doped with N-type impurities, and the ohmic surface It is also possible to form the conductive metal electrode in a single layer. In this case, although the light extraction efficiency in the direction of the back surface of the substrate is limited, a sufficient ohmic connection can be obtained between the semiconductor layer and the electrode, so that a light-emitting element having no problem in electrical characteristics can be obtained, and a single wafer can be used. Therefore, a gallium nitride-based compound semiconductor light emitting device excellent in mass productivity can be provided.

Further, the ohmic electrode 25a may be a translucent ohmic metal thin film. In this case, light can be efficiently extracted also from the P-type gallium nitride-based compound semiconductor layer 24 side. Further, the ohmic metal thin film 26 may be an opaque ohmic electrode. In this case, light is not emitted from the upper and lower directions of the light emitting element chip. By using
It is suitable for use in a chip component type light emitting device in which a chip is mounted on a circuit wiring board or the like without using metal wires by solder reflow, dipping, or the like.

The above-mentioned ohmic electrode 25a is applicable to other embodiments of the present invention such as the first embodiment. Even when the present invention is applied to another embodiment of the present invention, the spread of the current in the semiconductor layer under the formation of the ohmic electrode 25a can be ensured, and the current spreads and flows throughout the light emitting layer, so that the luminous efficiency is improved.

Next, a specific method for manufacturing a gallium nitride-based compound semiconductor light emitting device according to the second embodiment will be described in detail.

FIGS. 4A to 4C are process diagrams showing a method for manufacturing a gallium nitride-based compound semiconductor light emitting device using the second embodiment of the present invention.

As shown in FIG. 4A, the sapphire substrate 2
A stacked structure in which an N-type gallium nitride-based compound semiconductor layer 22, a gallium nitride-based compound semiconductor light-emitting layer 23, and a P-type gallium nitride-based compound semiconductor layer 24 are sequentially formed on 1 is formed. Here, an N-type gallium nitride-based compound semiconductor layer 22a doped with an N-type impurity at a high concentration is formed between the substrate 21 and the N-type gallium nitride-based compound semiconductor layer 22. Next, on the P-type gallium nitride-based compound semiconductor layer 24, for example, Au is usually formed on the order of μm as the ohmic electrode 25a, but when it is used as an ohmic metal thin film, for example, Ni is formed to a thickness of 7 nm. Ohmic electrode 25
a pad electrode 2 for making an electrical connection with the outside
As No. 5, Au is formed to a thickness of 0.6 μm.

Next, as shown in FIG. 4B, after the substrate 21 is polished to a thickness of about 100 μm, a separation groove 29 is formed on the back surface of the substrate 21 by, for example, wet etching, dry etching, dicing, or the like. It is formed by scribing or the like. Further, a second separation groove (not shown) is also formed in a direction perpendicular to the separation groove 29. The formation of the separation groove 29 and the second separation groove is performed until the N-type gallium nitride-based compound semiconductor layer 22 is exposed.

Next, as shown in FIG. 4C, the back surface and the side surface of the substrate 21, the side surface of the N-type gallium nitride-based compound semiconductor layer 22a doped with the N-type impurity at a high concentration, and the N-type gallium nitride-based On the surface of the compound semiconductor layer 22, Ni is formed to a thickness of 10 nm as a translucent ohmic metal thin film. Next, on the ohmic metal thin film 26, a 10 μm-thick layer of In ₂ O ₃ using Sn as a dopant is formed as the light-transmitting oxide semiconductor layer 27.

The gallium nitride-based compound semiconductor light-emitting device manufactured by the above-described method is scribed into a chip by scribing 300 μm square from the growth surface side.

As described above, by using the back electrode structure of the present invention for the back electrode of the substrate, the metal electrode does not break or become thin on the side surface of the substrate, and the electrode does not have high resistance. A gallium nitride-based compound semiconductor light emitting device that can reduce the voltage and easily supply an external current to the chip, and can form one electrode on the back surface of the substrate to reduce the chip area, and is inexpensive and excellent in mass productivity Can be produced.

<Third Embodiment> A gallium nitride-based compound semiconductor light emitting device according to a third embodiment of the present invention will be described with reference to FIG.

FIG. 5 is a sectional structural view of a gallium nitride-based compound semiconductor light emitting device manufactured by using the third embodiment of the present invention.

As shown in FIG. 5, an N-type gallium nitride-based compound semiconductor layer 32, a gallium nitride-based compound semiconductor light-emitting layer 33, and a P-type gallium nitride-based compound semiconductor layer 34 are sequentially laminated on, for example, a sapphire substrate 31. A laminated structure is formed. Here, between the substrate 31 and the N-type gallium nitride-based compound semiconductor layer 32, for example, Si, Ge, Sn,
A group IV or group VI N-type impurity such as S, Se, Te, etc.
An N-type gallium nitride-based compound semiconductor layer 32a doped at a high concentration of 10 ¹⁷ to 1 × 10 ²¹ cm ⁻³ is formed.
The light emitting layer includes a single quantum well and a multiple quantum well light emitting layer. Although the present invention may use a conductive substrate such as GaN or SiC, the present invention is most effective when used for an insulating or translucent substrate such as the sapphire substrate 31.

On the P-type gallium nitride-based compound semiconductor layer 34, a pad electrode 35 for making electrical connection with the outside such as a lead frame or a circuit wiring board is formed. The pad electrode 35 is made of, for example, Au, Au alloy, A
The thickness is set to 0.5 μm or more and 0.8 μm or less in order to prevent electrode peeling during bonding. Note that a P-type gallium nitride-based compound semiconductor contact layer may be formed between the pad electrode 35 and the P-type gallium nitride-based compound semiconductor layer 34 in order to obtain good conductivity.

The back surface of the substrate 31 and the N-type gallium nitride-based compound semiconductor layer 32a heavily doped with N-type impurities
An ohmic metal thin film 36 having a light-transmitting property is formed on the upper side. For example, Au, N
i, Ti, Pt, Pd, etc. are formed using a vacuum evaporation method, an electron beam evaporation method, or the like. Further, a light-transmitting oxide semiconductor layer 37 is formed on the ohmic metal thin film 36 including the side surface of the substrate 31. The oxide semiconductor layer 37 is formed of I
n ₂ O ₃ , SnO ₂ , ZnO, Cd ₂ SnO ₄ , CdSnO ₃
Consisting of one of the following: evaporation method, sputter method, CVD
It is formed using a method or the like. Note that the thickness of the oxide semiconductor layer 37 is preferably in the range of 5 μm to 15 μm in consideration of securing the film thickness on the side surface of the substrate and light transmittance of 40% or more. Further, even if In ₂ O ₃ to which Ti is added is used as the oxide semiconductor layer 37, Ti may be added because the film resistance and the transmittance do not deteriorate.

For electrical connection between the pad electrode 35 and the outside, a metal wire 38 of, for example, Au, Al, Cu or the like is used. On the other hand, for electrical connection between the ohmic metal thin film 36 and the oxide semiconductor layer 37 and the outside, for example, solder, A
g paste, conductive adhesive or the like is used.

As described above, the N-type gallium nitride-based compound semiconductor layer 32a doped with the N-type impurity at a high concentration is formed on the back surface and the side surface of the substrate 31 where the electrode is disconnected and the thickness of the electrode is increased and the resistance of the electrode is increased. By sequentially forming the ohmic metal thin film 36 and the oxide semiconductor layer 37 on the top, a light-emitting element having no problem in electrical characteristics can be obtained, the light extraction efficiency can be increased, and a single wafer can be obtained. Therefore, a gallium nitride-based compound semiconductor light emitting device excellent in mass productivity can be provided. Also, the substrate 31
Since only the light-transmitting oxide semiconductor layer 37 is formed on the side surface, light can be efficiently extracted to the outside.

The gallium nitride-based compound semiconductor light-emitting device having the above-described structure has been described with reference to a light-emitting device having a homostructure. However, a gallium nitride-based compound semiconductor light-emitting device may have a double heterostructure, a single heterostructure, or an active layer. Needless to say, the present invention can be applied to any structure such as a quantum well structure.

Further, the ohmic metal thin film 36 may be an opaque ohmic electrode. In this case, it is not necessary to form the oxide semiconductor layer 37 over the entire surface of the ohmic electrode, However, it is sufficient that they are in contact with each other so that electrical continuity can be obtained, and connection with a circuit wiring board or the like can be reliably performed at the ohmic electrode portion. Further, light in the direction of the substrate 31 can be efficiently extracted from the side surface of the substrate 31.

Next, a specific method for manufacturing a gallium nitride-based compound semiconductor light emitting device according to the third embodiment will be described in detail.

FIGS. 6A to 6C are process diagrams showing a method of manufacturing a gallium nitride-based compound semiconductor light emitting device using the third embodiment of the present invention.

As shown in FIG. 6A, the sapphire substrate 3
A stacked structure in which an N-type gallium nitride-based compound semiconductor layer 32, a gallium nitride-based compound semiconductor light-emitting layer 33, and a P-type gallium nitride-based compound semiconductor layer 34 are sequentially formed on 1 is formed. Here, an N-type gallium nitride-based compound semiconductor layer 32a doped with an N-type impurity at a high concentration is formed between the substrate 31 and the N-type gallium nitride-based compound semiconductor layer 32. Next, on the P-type gallium nitride-based compound semiconductor layer 34, Au is formed to a thickness of 0.5 μm as a pad electrode 35 for making an electrical connection to the outside.

Next, as shown in FIG. 6B, after the substrate 31 is polished to a thickness of about 100 μm, a separation groove 39 is formed on the back surface of the substrate 31 by, for example, wet etching, dry etching, dicing, or the like. It is formed by scribing or the like. Further, a second separation groove (not shown) is also formed in a direction perpendicular to the separation groove 39. The formation of the separation groove 39 and the second separation groove is performed by forming the N-type gallium nitride-based compound semiconductor layer 3 doped with an N-type impurity at a high concentration.
Repeat until 2a is exposed.

Next, as shown in FIG. 6C, an ohmic ohmic material having a light-transmitting property is formed on the back surface of the substrate 31 and on the N-type gallium nitride-based compound semiconductor layer 32a doped with an N-type impurity at a high concentration. As the conductive metal thin film 36, Pd is formed in a thickness of 1 to 3 nm, or Ti and Au are formed in a thickness of 3 nm and 4 nm, respectively.
Next, on the ohmic metal thin film 36 including the side surface of the substrate 31, as a light-transmitting oxide semiconductor layer 37, In ₂ O ₃
Then, a layer using Sn as a dopant is formed to a thickness of 10 μm. Alternatively, Ti ₂ -added In ₂ O ₃ may be used.

The gallium nitride-based compound semiconductor light emitting device manufactured by the above manufacturing method is chipped by scribing from a growth surface side into a square of 250 μm.

As described above, by forming the back electrode of the substrate with the back electrode configuration of the present invention, light can be effectively radiated from the back surface of the substrate to the outside without light being blocked by the back electrode of the substrate. And the light emission output can be increased. In addition, the metal electrodes do not break or become thinner on the side surfaces of the substrate, so that the electrodes do not increase in resistance, the forward voltage can be reduced, and an external current can be easily supplied to the chip. Since the electrodes can be formed on the back surface of the substrate, the chip area can be reduced, and a gallium nitride based compound semiconductor light emitting device which is inexpensive and excellent in mass productivity can be manufactured.

<Fourth Embodiment> A gallium nitride-based compound semiconductor light emitting device according to a fourth embodiment of the present invention will be described with reference to FIG.

FIG. 7 is a cross-sectional structural view of a gallium nitride-based compound semiconductor light emitting device manufactured by using the fourth embodiment of the present invention.

As shown in FIG. 7, the element structure of the present invention basically has a structure in which the element structure of the first embodiment is turned upside down.

That is, for example, on a sapphire substrate 41, N
A stacked structure is formed in which the gallium nitride-based compound semiconductor layer 42, the gallium nitride-based compound semiconductor light emitting layer 43, and the p-type gallium nitride-based compound semiconductor layer 44 are sequentially stacked. Here, the substrate 41 and the N-type gallium nitride-based compound semiconductor layer 4
2, for example, Si, Ge, Sn, S, Se, T
e or another group IV or group VI N-type impurity in the range of 1 × 10 ¹⁷ to 1 ×
An N-type gallium nitride-based compound semiconductor layer 42a doped at a high concentration of 10 ²¹ cm ^-3 is formed. The light emitting layer includes a single quantum well and a multiple quantum well light emitting layer. In the present invention, a conductive substrate such as GaN or SiC can be used.
The present invention is most effective when used for a light-transmitting substrate.

On the P-type gallium nitride-based compound semiconductor layer 44, an ohmic electrode 45a for making an electrical connection with the outside such as a lead frame or a circuit wiring board is formed. The ohmic electrode 45a is made of, for example, Ni-A
u, Au alloy, Al, etc., and the thickness is 0.5 μm to prevent electrode peeling during bonding.
It is formed to have a thickness of at least 100 μm. The ohmic electrode 45
A P-type gallium nitride compound semiconductor contact layer may be formed between a and the P-type gallium nitride compound semiconductor layer 44 in order to obtain good conductivity.

An ohmic metal thin film 46 having a light-transmitting property is formed on the back and side surfaces of the substrate 41 and on the N-type gallium nitride-based compound semiconductor layer 42a heavily doped with N-type impurities.
And a light-transmitting oxide semiconductor layer 47 are sequentially formed. For example, Au, N
i, Ti, Pt, Pd, etc. are formed to have a film thickness of 1 nm or more and 10 nm or less in order to satisfy a small film resistance and a large transmittance by using a vacuum evaporation method, an electron beam evaporation method, or the like. The oxide semiconductor layer 47 is made of In ₂ O ₃ , Sn
It is made of one of O ₂ , ZnO, Cd ₂ SnO ₄ , and CdSnO ₃ and is formed by using a vapor deposition method, a sputter method, a CVD method, or the like. Note that the thickness of the oxide semiconductor layer 47 is preferably in a range of 5 μm to 15 μm in consideration of securing the thickness on the side surface of the substrate and light transmittance of 40% or more.
In addition, Ti ₂ -added In ₂ O _{3 is} used for the oxide semiconductor layer 47.
Since Ti does not deteriorate the film resistance and transmittance even if Ti is used, Ti may be added.

A pad electrode 45 is formed on a part of the oxide semiconductor layer 47 for making an electrical connection with the outside such as a lead frame and a circuit wiring board. The pad electrode 45 is made of, for example, Au, an Au alloy, Al, or the like, and has a thickness of 0.5 μm or more and 0.8 μm or less in order to prevent electrode peeling during bonding. For electrical connection between the pad electrode 45 and the outside, a metal wire 48 of, for example, Au, Al, or Cu is used.
On the other hand, for the electrical connection between the ohmic electrode 45a and the outside,
For example, solder, Ag paste, conductive adhesive, or the like is used.

Although the pad electrode 45 is located on the substrate surface in FIG. 7, the pad electrode 45 can be formed at an arbitrary position on the oxide semiconductor layer 47 as long as conduction can be obtained. Also, pad electrode 4
It is not always necessary that the oxide semiconductor layer 47 immediately below 5 is formed, and the oxide semiconductor layer 47 may be formed on the ohmic metal thin film 46 or a part thereof may be formed directly on the semiconductor layer.

As described above, by using the back surface of the substrate as the upper portion, the mounting surface becomes substantially flat when the light emitting element chip is mounted on a lead frame, a circuit wiring board, or the like. It also contributes to improving the registration system.

The gallium nitride-based compound semiconductor light-emitting device having the above structure has been described with reference to a light-emitting device having a homostructure. Needless to say, the present invention can be applied to any structure such as a quantum well structure.

<Fifth Embodiment> A gallium nitride based compound semiconductor light emitting device according to a fifth embodiment of the present invention will be described with reference to FIGS.

FIG. 8 is a sectional structural view of a gallium nitride-based compound semiconductor light emitting device manufactured by using the fifth embodiment of the present invention.

FIG. 9 is a sectional structure diagram of a gallium nitride based compound semiconductor light emitting device manufactured by using the fifth embodiment of the present invention, which is close to the actual scale.

FIG. 10 is a schematic sectional view showing a case where a gallium nitride-based compound semiconductor light emitting device manufactured by using the fifth embodiment of the present invention is mounted on a lead frame.

As shown in FIG. 8, the element structure of the present invention basically has a structure in which the element structure of the third embodiment is turned upside down.

That is, for example, on the sapphire substrate 51, N
A stacked structure is formed in which a gallium nitride-based compound semiconductor layer 52, a gallium nitride-based compound semiconductor light emitting layer 53, and a p-type gallium nitride-based compound semiconductor layer 54 are sequentially stacked. Here, the substrate 51 and the N-type gallium nitride-based compound semiconductor layer 5
2, for example, Si, Ge, Sn, S, Se, T
e or another group IV or group VI N-type impurity in the range of 1 × 10 ¹⁷ to 1 ×
An N-type gallium nitride-based compound semiconductor layer 52a doped at a high concentration of 10 ²¹ cm ^-3 is formed. The light emitting layer includes a single quantum well and a multiple quantum well light emitting layer. In the present invention, a conductive substrate such as GaN or SiC can be used.
The present invention is most effective when used for a light-transmitting substrate.

On the P-type gallium nitride-based compound semiconductor layer 54, an ohmic electrode 55a for making an electrical connection with the outside such as a lead frame or a circuit wiring board is formed. The ohmic electrode 55a is made of, for example, Ni-A
u, Au alloy, Al, etc., and the thickness is 0.5 μm to prevent electrode peeling during bonding.
It is formed to have a thickness of at least 100 μm. The ohmic electrode 55
A P-type gallium nitride compound semiconductor contact layer may be formed between a and the P-type gallium nitride compound semiconductor layer 54 in order to obtain good conductivity.

On the back surface of the substrate 51 and at a high concentration of N-type impurities
Doped N-type gallium nitride-based compound semiconductor layer 52a
An ohmic metal thin film 56 having a light-transmitting property is formed thereon.
Have been. For example, Au, N
i, Ti, Pt, Pd, etc. are deposited by vacuum evaporation, electron beam evaporation.
It is formed using a deposition method or the like. For example, ohmic metal thin film 5
6 to form Pd of 1 to 3 nm, or Ti and Au
And 2.5 nm and 1 nm, respectively. Further, the substrate 51
On the ohmic metal thin film 56 including the side surfaces of
Oxide semiconductor layer 57 is formed. Oxide semiconductor
Layer 57 comprises In _TwoO_Three, SnO_Two, ZnO, Cd_TwoSn
O_Four, CdSnO_ThreeConsisting of one of
It is formed using a pattering method, a CVD method, or the like. In addition, oxide half
The thickness of the conductor layer 57 depends on the thickness on the side of the substrate and the light transmittance.
Considering securing 40% or more, preferably 5 μm
The range is preferably from m to 15 μm. In addition, the oxide semiconductor layer 57
In with Ti added as_TwoO_ThreeEven if using membrane resistance, transmission
Since the rate does not deteriorate, Ti may be added.

A pad electrode 55 is formed on a part of the oxide semiconductor layer 57 for making electrical connection with the outside such as a lead frame and a circuit wiring board. The pad electrode 55 is made of, for example, Au, an Au alloy, Al, or the like, and has a thickness of 0.5 μm or more and 0.8 μm or less in order to prevent electrode peeling during bonding. For electrical connection between the pad electrode 55 and the outside, for example, a metal wire 58 of Au, Al, Cu or the like is used.
On the other hand, for the electrical connection between the ohmic electrode 55a and the outside,
For example, solder, Ag paste, conductive adhesive, or the like is used.

Although the pad electrode 55 is located on the substrate surface in FIG. 8, the pad electrode 55 can be formed at an arbitrary position on the oxide semiconductor layer 57 as long as conduction can be obtained. In addition, pad electrode 5
It is not always necessary that the oxide semiconductor layer 57 immediately below 5 is formed, and the oxide semiconductor layer 57 may be formed on the ohmic metal thin film 56 or a part thereof may be formed directly on the semiconductor layer.

As described above, by using the back surface of the substrate as the upper portion, the mounting surface becomes substantially flat when the light emitting element chip is mounted on a lead frame, a circuit wiring board, or the like. It also contributes to improving the registration system. Further, since only the light-transmitting oxide semiconductor layer 57 is formed on the side surface of the substrate 51, light can be efficiently extracted to the outside.

The gallium nitride-based compound semiconductor light emitting device having the above structure has been described as a light emitting device having a homo structure. However, a gallium nitride based compound semiconductor light emitting device having a double hetero structure, a single hetero structure or an active layer may be used. Needless to say, the present invention can be applied to any structure such as a quantum well structure.

FIG. 9 shows a gallium nitride-based compound semiconductor light emitting device chip manufactured by using the fifth embodiment of the present invention in a cross-sectional shape on a scale close to a substantially actual shape.

As shown in FIG. 9, the actual light emitting element chip has an overwhelmingly larger shape of the substrate 51 than the semiconductor layer portion 59, the ohmic metal thin film 56, and the oxide semiconductor layer 57. Therefore, when the translucent ohmic metal thin film 56 is formed on the back surface of the substrate 51 and on the N-type gallium nitride-based compound semiconductor layer 52a highly doped with N-type impurities, the ohmic metal thin film 56 Is particularly thin, and there are island-shaped or non-formed regions. Also in this case, since the oxide semiconductor layer 57 is formed on the ohmic metal thin film 56, the conductivity is sufficiently ensured. Even if the ohmic metal thin film 56 becomes thicker and becomes a partially opaque ohmic metal electrode, light is sufficiently radiated to the outside. Further, since only the oxide semiconductor layer 57 is formed on the side surface of the substrate 51, light is emitted from the side surface of the substrate 51 without being blocked.

FIG. 10 shows an example in which a gallium nitride-based compound semiconductor light emitting device chip manufactured by using the fifth embodiment of the present invention is mounted on a lead frame for the purpose of electrical connection with the outside. .

As shown in FIG. 10, the light radiated from the side surface 51a of the substrate is radiated to the cup 59a of the lead frame 59 without being interrupted, and the light is radiated upward. Therefore, a gallium nitride-based compound semiconductor light-emitting device that extracts light from the substrate surface side without reducing external luminous efficiency can be easily manufactured.

According to the above configuration, the back and side surfaces of the substrate can be used as a light-transmitting surface, and the substrate back surface electrode is formed of a translucent ohmic metal thin film. A gallium nitride-based compound semiconductor light emitting device that can effectively emit light to the outside from the back and side surfaces, has good light extraction efficiency to the outside, can increase light emission output, can reduce the chip area, is inexpensive, and has excellent mass productivity Can be produced.

<Sixth Embodiment> Referring to FIG. 11, a fifth embodiment of a gallium nitride based compound semiconductor light emitting device according to the present invention will be described.
An embodiment will be described.

FIG. 11 is a sectional structural view of a gallium nitride-based compound semiconductor light emitting device manufactured by using the fifth embodiment of the present invention.

As shown in FIG. 11, the device structure of the present invention has a light-transmitting property on the back and side surfaces of the substrate 61 and on the N-type gallium nitride-based compound semiconductor layer 62a heavily doped with N-type impurities. The element structure is basically the same as that of the fourth embodiment except that no ohmic metal thin film is formed.

According to this structure, the surface of the substrate 61 is used as a light-transmitting surface, and the light-transmitting oxide semiconductor layer 67 is used.
The N-type gallium nitride-based compound semiconductor layer 62a doped with the N-type impurity at a high concentration
Since it is formed directly on the upper side, the step of forming an ohmic metal thin film is not required, and the substrate back surface electrode can be formed more easily.

However, the forward voltage of the light emitting element is higher by about 0.5 V than the light emitting element according to the other embodiments of the present invention. However, since the ohmic metal thin film is not formed, light can be more effectively emitted from the back side of the substrate to the outside than in the other embodiments, so that light extraction efficiency to the outside is good, the light emission output can be increased, and the chip can be increased. A gallium nitride-based compound semiconductor light emitting device which can be reduced in area, inexpensive and excellent in mass productivity can be manufactured.

[0116]

According to the present invention, in the gallium nitride-based compound semiconductor light emitting device, one of the pad electrodes, which had conventionally been required to be formed on the same surface, can be formed on the back surface of the substrate. Short-circuit failure and appearance defect or the like that occurred during the wire bonding step can be prevented. Further, since the area of the light emitting element chip can be reduced, the number of chips that can be obtained from one wafer can be increased. Therefore, the device characteristics, reliability, and yield can be improved, and the price of the final product can be reduced. Further, the spread of current on the first conductivity type gallium nitride-based compound semiconductor layer side is ensured, a good ohmic connection is obtained, and the emission efficiency can be improved. Accordingly, the efficiency of light emission immediately below the substrate and the overall light extraction efficiency is improved.

Further, since the entire back surface of the substrate can be used for electrical connection with the outside, there is no occurrence of poor electrical connection with the outside due to a gap between the lead frame for mounting the light emitting element chip and the mounting substrate. Therefore, improvements in element characteristics, reliability, and yield are achieved. Further, it is not necessary to perform special processing on the lead frame or the mounting board, and the conventional lead frame or mounting board can be used as it is.
Therefore, the manufacturing cost can be reduced.

In addition, the spread of current on both sides of the gallium nitride-based compound semiconductor layer of the first conductivity type and the gallium nitride-based compound semiconductor layer of the second conductivity type is ensured, and evenly on the substrate surface where current does not easily flow. Since the current is diffused, uniform light emission is performed as a whole, and light emission efficiency can be improved.
Therefore, the efficiency of light emission immediately below the substrate and the overall light extraction efficiency is improved.

When the oxide semiconductor layer is used alone as the ohmic electrode, the forward voltage slightly increases, but the manufacturing process is simplified because the ohmic metal electrode need not be formed.

[Brief description of the drawings]

FIG. 1 is a sectional structural view of a gallium nitride-based compound semiconductor light emitting device according to a first embodiment.

FIGS. 2A to 2C are process diagrams illustrating a method for manufacturing a gallium nitride-based compound semiconductor light emitting device according to the first embodiment of the present invention.

FIG. 3 is a sectional structural view of a gallium nitride-based compound semiconductor light emitting device according to a second embodiment.

FIGS. 4A to 4C are process diagrams illustrating a method for manufacturing a gallium nitride-based compound semiconductor light emitting device according to a second embodiment of the present invention.

FIG. 5 is a sectional structural view of a gallium nitride-based compound semiconductor light emitting device according to a third embodiment.

FIGS. 6A to 6C are process diagrams showing a method for manufacturing a gallium nitride-based compound semiconductor light emitting device according to a third embodiment of the present invention.

FIG. 7 is a sectional structural view of a gallium nitride-based compound semiconductor light emitting device according to a fourth embodiment.

FIG. 8 is a sectional structural view of a gallium nitride-based compound semiconductor light emitting device according to a fifth embodiment.

FIG. 9 is a cross-sectional view of a gallium nitride-based compound semiconductor light emitting device according to a fifth embodiment, which is close to the actual scale.

FIG. 10 is a schematic cross-sectional view when a gallium nitride-based compound semiconductor light emitting device according to a fifth embodiment is mounted on a lead frame.

FIG. 11 is a sectional structural view of a gallium nitride-based compound semiconductor light emitting device according to a sixth embodiment.

FIG. 12 is a sectional structural view of a conventional gallium nitride-based compound semiconductor light emitting device.

FIG. 13 is a sectional structural view of another conventional gallium nitride-based compound semiconductor light emitting device.

FIG. 14 is a sectional structural view of another conventional gallium nitride-based compound semiconductor light emitting device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 N-type gallium nitride compound semiconductor layer 2a Layer containing high concentration N-type impurity 3 Gallium nitride compound semiconductor light emitting layer 4 P-type gallium nitride compound semiconductor layer 5 Pad electrode 6 Ohmic metal thin film 7 Oxide semiconductor Layer 8 metal wire

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tsuyoshi Kankawa 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Inside Sharp Corporation (72) Inventor Kensaku Yamamoto 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka F term in reference (reference) 5F041 AA03 AA05 AA25 AA41 AA43 CA02 CA03 CA04 CA05 CA34 CA40 CA46 CA57 CA74 CA76 CA82 CA83 CA93 CA98 DA02 DA03 DA08 DA18 DA26

Claims (9)

[Claims] 1. A gallium nitride-based compound semiconductor light-emitting device formed on a substrate and having a laminated structure having at least a first conductivity-type gallium nitride-based compound semiconductor layer, a light-emitting layer, and a second conductivity-type gallium nitride-based compound semiconductor layer. A layer containing a high-concentration first-conductivity-type impurity is formed between the substrate and the first-conductivity-type gallium nitride-based compound semiconductor layer, and the back surface of the substrate opposite to the surface on which the multilayer structure is formed; Is removed to a depth that reaches at least the layer containing the high concentration first conductivity type impurity, and an ohmic electrode is formed on the substrate back surface and on the layer containing the high concentration first conductivity type impurity. A gallium nitride-based compound semiconductor light emitting device, which is formed. 2. The semiconductor device according to claim 1, wherein the ohmic electrode is continuously formed also on a step side surface between the back surface of the substrate and the layer containing the high-concentration first conductivity type impurity.
3. The gallium nitride-based compound semiconductor light-emitting device according to item 1. 3. A gallium nitride-based compound semiconductor light emitting device formed on a substrate and having a laminated structure having at least a first conductivity type gallium nitride-based compound semiconductor layer, a light emitting layer, and a second conductivity type gallium nitride-based compound semiconductor layer. A layer containing a high-concentration first-conductivity-type impurity is formed between the substrate and the first-conductivity-type gallium nitride-based compound semiconductor layer, and the back surface of the substrate opposite to the surface on which the multilayer structure is formed; Is removed at least to a depth reaching the first conductivity type gallium nitride-based compound semiconductor layer,
An ohmic electrode is formed on the back surface of the substrate, on the back surface of the gallium nitride-based compound semiconductor layer of the first conductivity type, and on the gallium nitride-based compound semiconductor layer of the second conductivity type. Compound semiconductor light emitting device. 4. The ohmic metal electrode is formed on the ohmic metal electrode and on the first conductivity type gallium nitride-based compound semiconductor layer, and on the back surface of the substrate and the high concentration first conductivity type. The gallium nitride-based compound semiconductor light emitting device according to claim 3, wherein the gallium nitride-based compound semiconductor light emitting device is also formed continuously on the side surface of the layer containing the impurity. 5. The ohmic electrode according to claim 1, wherein the ohmic electrode has a multilayer structure including an ohmic metal electrode and a light-transmitting oxide semiconductor layer. Gallium nitride based compound semiconductor light emitting device. 6. The ohmic metal electrode is formed at least on the back surface of the substrate and on a layer containing the high-concentration first conductivity type impurity, and the oxide semiconductor layer is formed on the ohmic metal electrode. The gallium nitride-based material according to claim 5, wherein the gallium nitride-based material is formed continuously on a step side surface between the back surface of the substrate and the layer containing the high concentration first conductivity type impurity. Compound semiconductor light emitting device. 7. The ohmic metal electrode is formed at least on the back surface of the substrate and on the first conductivity type gallium nitride-based compound semiconductor layer, and the oxide semiconductor layer comprises:
It is formed on the ohmic metal electrode and on the first conductivity type gallium nitride-based compound semiconductor layer, and continuously on the back surface of the substrate and on the side surface of the layer containing the high concentration first conductivity type impurity. The gallium nitride-based compound semiconductor light emitting device according to claim 5, wherein the light emitting device is formed of: 8. The method according to claim 5, wherein the ohmic metal electrode is formed of a translucent ohmic metal thin film.
8. The gallium nitride-based compound semiconductor light-emitting device according to any one of items 1 to 7. 9. A gallium nitride-based compound semiconductor light emitting device comprising a laminated structure formed on a substrate and having at least a first conductivity type gallium nitride-based compound semiconductor layer, a light emitting layer, and a second conductivity type gallium nitride-based compound semiconductor layer. In the manufacturing method, a step of forming a layer containing high-concentration first-conductivity-type impurities between the substrate and the first-conductivity-type gallium nitride-based compound semiconductor layer; and opposing a surface on which the laminated structure is formed. Removing a part of the substrate backside at least to a depth that reaches the layer containing the high-concentration first conductivity-type impurity, on the substrate backside and on the layer containing the high-concentration first conductivity-type impurity Forming a gallium nitride-based compound semiconductor light emitting device.