JP2002084001A - Group iii nitride semiconductor light emitting diode, light emitting diode lamp, light source, electrode for group iii nitride semiconductor light emitting diode and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem where an LED driving current is supplied from only a pedestal electrode serving as an ohmic electrode in the conventional group III nitride semiconductor LED, so that the driving current cannot be diffused in a wide domain of a light emitting region, and a group III nitride semiconductor LED having high luminous intensity is not provided suitably. SOLUTION: A surface ohmic electrode, a window layer composed of a conductive transparent oxide crystal layer and the pedestal electrode are formed on a surface layer of a laminated structure which is laminated on a conductive substrate via a boron phosphide(BP) based buffer layer. As a result, the driving current is diffused in the wide domain of the light emitting region, and the group III nitride semiconductor LED having high luminous intensity is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a group III nitride semiconductor light emitting diode (LED) having an ohmic electrode arrangement suitable for diffusing a device driving current over a wide range of a light emitting region, and its use. I
The present invention relates to a group II nitride semiconductor light emitting diode electrode and a method for manufacturing the same.

[0002]

2. Description of the Related Art A group III nitride semiconductor light emitting diode is, for example, aluminum gallium indium (Al _x Ga _y In _{1 -XY} N: 0 ≦ X, Y ≦ 1, 0 ≦ X +
Y ≦ 1) and the like. Generally, a buffer is used in the laminated structure in order to reduce the lattice mismatch between the substrate material and the group III nitride semiconductor layer forming the laminated structure and grow a high-quality group III nitride semiconductor layer. ) Layer (see JP-A-2-229476). In a laminated structure for a light-emitting element using sapphire (α-Al ₂ O ₃ single crystal) as a substrate, the buffer layer is exclusively made of aluminum gallium nitride (composition formula: Al _α Ga _β N: 0 ≦
α, β ≦ 1) (see JP-A-2-22)
9476). An electrode for supplying an element driving current to an LED having such a laminated structure, a so-called electrode,
In a laminated structure using an insulating material such as sapphire as a substrate, the ohmic electrode is disposed on the p-type conductive layer and the n-type conductive layer constituting the laminated structure (for example, Kaihei 6-260682).

FIG. 1 shows a structure in which Al _{α is formed} on a sapphire substrate 101.
Ga _β N (0 ≦ α, β ≦ 1, α + β = 1) buffer layer 102
, A lower cladding layer 103 made of n-type gallium nitride (GaN) and a gallium indium nitride (G
a _Y In _1-Y N: 0 ≦ Y ≦ 1), a light emitting layer 104, and a p-type GaN upper cladding layer 105, p
1 schematically illustrates a cross-sectional structure of a conventional group III nitride semiconductor LED 100 including a light emitting unit 10 having an n-junction type double hetero (DH) structure. Since the substrate 101 is insulating, p
Each of the n-type and n-type ohmic electrodes 106 and 107 needs to be provided on the surfaces of the p-type conductive layer (p-type cladding layer 105) and the n-type conductive layer (n-type cladding layer 103) which form a laminated structure. That is, the electrode 107 is formed through complicated processing for cutting a part of the light emitting unit 10. Light emitting unit 1
Since a part of 0 is removed, the surface area of the light emitting unit 10 is reduced, and there is a disadvantage that a group III nitride semiconductor LED having high emission intensity cannot be provided.

On the other hand, there is also known an example in which a conductive crystal such as gallium phosphide (GaP) or silicon (silicon) is used as a substrate to form a laminated structure for use in a group III nitride semiconductor blue LED (Japanese Patent Laid-Open No. 2-210). 275682).
In forming this laminated structure, boron phosphide (BP)
A technique for forming a buffer layer from a system material is disclosed (see Japanese Patent Application Laid-Open No. 2-275682). In a laminated structure using a conductive crystal as a substrate, an electrode of a first conductivity type corresponding to the conductivity type of the substrate crystal is provided on the back surface of the substrate, and an electrode of a second conductivity type opposite to the electrode is formed on the substrate crystal. It is customary to dispose it on a layer constituting a laminate of the opposite conductivity type.
-247761). In this conventional electrode arrangement example, it is not necessary to remove the light emitting portion provided on the substrate surface, so that the surface area of the light emitting portion does not decrease. It has an advantage in the first place.

A conventional III group ohmic electrode having a first conductive type ohmic electrode (backside ohmic electrode) on the back surface of a conductive substrate and a second conductive type ohmic electrode (front surface ohmic electrode) on the surface of the laminated structure. Nitride semiconductor LED 200
2 is schematically illustrated in FIG. In general, the surface ohmic electrode 201 is also disposed solely at the center of one constituent layer 202 of the laminated structure, also serving as an electrode (pedestal electrode) for connection (bonding) (see Japanese Unexamined Patent Publication No. Hei 2-27).
No. 5682). Further, a conventional example is known in which a band-shaped electrode directly in contact with a pedestal electrode at the center is attached to form a surface ohmic electrode (Japanese Patent Laid-Open No. 11-1682).
No. 40).

Conventionally, the surface ohmic electrode has been exclusively made of aluminum gallium nitride (Al _x Ga _y N: 0 ≦ X,
(Y ≦ 1, X + Y = 1) Usually, it is provided on a crystal layer (see Japanese Patent Application Laid-Open No. 6-314822). However, aluminum nitride (AlN) and gallium nitride (G
aN) has a mobility of other I such as gallium arsenide (GaAs) or indium phosphide (InP).
An order of magnitude smaller than that of II-V compound semiconductors (Yasuharu Suematsu, “Optical Device” (May 15, 1997)
(Corporation of Corona Co., Ltd., first edition, 8th press), pages 28-29). For example, the hole mobility at room temperature of aluminum nitride (AlN) is 14 cm ² / V · s, for example, 500 cm ² / V · s of indirect transition type boron phosphide (BP).
(See "Optical Device", pp. 28-29). For this reason, the conventional electrode disposing means in which only the ohmic electrode is provided on the constituent layer cannot sufficiently diffuse the element operating current over a wide range of the light emitting portion, and is disadvantageous in obtaining a high-strength group III nitride semiconductor LED. Has become.

[0007] In view of the physical properties of a group III nitride semiconductor, which is inferior to other group III-V compound semiconductors in terms of current diffusivity, in the prior art, in order to diffuse the device operating current over a wide range, it is directly connected to a pedestal electrode. Means for utilizing the light-transmitting metal thin film electrode as an ohmic electrode has been disclosed (see JP-A-6-314822). For example, gallium nitride (Ga) doped with a p-type impurity
N) gold (A) is formed on substantially the entire surface of the group III nitride semiconductor layer.
u) A light-transmitting ohmic electrode made of a thin film is provided (refer to the specification of JP-A-6-314822). However, in this conventional technique, since the light emitted from the light emitting portion is absorbed to a considerable extent by the metal thin film forming the electrode, there is a problem that the intensity of the emitted light that can be extracted to the outside of the LED is eventually reduced.

The indium-tin composite oxide (ITO) film has a higher transmittance to blue, green or longer wavelength light emitted from the group III nitride semiconductor LED than the above-mentioned metal thin film. ("Transparent conductive film technology"
(See Ohmsha Co., Ltd., published on March 30, 1999, 1st edition, 1st printing), pp. 97-101). In order to take out light emission to the outside by utilizing this transmittance, a conductive transparent oxide crystal layer made of ITO is provided as a contact layer (light emission transmission window layer) for the gallium nitride (GaN) layer and is made of Group III. Techniques for forming a nitride semiconductor LED are known (JP-A-49-122294, JP-A-6-38265, and Appl. Phys.
Lett. , Vol. 74, no. 26 (1999),
See pages 3930-3932.)

In the prior art, particularly high holes (ho)
le) It is frequently used to dispose a conductive transparent oxide crystal layer of ITO or the like on a p-type GaN layer which is difficult to obtain concentration and mobility and has poor current diffusivity (see Japanese Utility Model Application Laid-Open No. 6-38).
No. 265, and Appl. Phys. Lett. reference). However, the ohmic contact between the ITO and the group III nitride semiconductor crystal layer is not good, and there is a disadvantage that the forward voltage (Vf) increases in the above case (for details, see Appl. Ph.
ys. Lett. , Vol. 74 (1999)).

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned disadvantages of the prior art, and comprises a conductive transparent oxide crystal layer such as ITO as a window layer for efficiently extracting light emission to the outside. In the group III nitride semiconductor LED, the device operating current can be diffused over a wide range of the light emitting portion, and
Means for arranging ohmic electrodes for extracting high-intensity light emission to the outside is presented. It is another object of the present invention to provide a high-strength III-nitride semiconductor light-emitting diode having an ohmic electrode arranged by the means, an electrode for the III-nitride semiconductor light-emitting diode, and a method of manufacturing the same.

In particular, according to the present invention, a surface ohmic electrode is disposed at a suitable position on the surface of one constituent layer of the laminated structure with respect to the position of the pedestal electrode in order to widely diffuse the element operating current to the light emitting portion. The main point is to do.

[0012]

According to the present invention, there is provided: (1) a first conductivity type single crystal substrate having a back surface ohmic electrode of the first conductivity type, and a single crystal substrate formed on the surface of the single crystal substrate. A buffer layer made of boron phosphide (BP) -based material;
A gallium nitride (GaN) -based group III nitride crystal layer including a light-emitting portion having a heterojunction structure provided on the buffer layer;
A group III nitride semiconductor light emitting diode comprising at least a window layer made of a conductive transparent oxide crystal layer provided on the group III nitride crystal layer, wherein the surface of the group III nitride crystal layer and the window layer A surface ohmic electrode of the second conductivity type, which conducts with the window layer, is formed in contact with the surface of the group III nitride crystal layer, and a connection base is provided at the center of the upper surface of the window layer. A group III nitride semiconductor light emitting diode, wherein an electrode is formed. It is.

The present invention also provides: (2) The II according to (1), wherein the surface ohmic electrode is arranged around the pedestal electrode.
Group I nitride semiconductor light emitting diode. (3) The group III nitride semiconductor light-emitting diode according to (1) or (2), wherein the surface ohmic electrode is disposed at a position symmetrical with respect to the center of the pedestal electrode. (4) The group III nitride semiconductor light-emitting diode according to any one of (1) to (3), wherein the surface ohmic electrode is provided at a position equidistant from the center of the pedestal electrode. (5) The surface ohmic electrode is composed of a plurality of electrodes arranged at equal intervals. (1)
A group III nitride semiconductor light-emitting diode according to any one of (1) to (4). (6) The surface ohmic electrode is arranged on a region other than the projection region of the pedestal electrode on the surface of the group III nitride crystal layer (hereinafter, referred to as an open light-emitting region). The group III nitride semiconductor light-emitting diode according to (5). (7) The group III nitride semiconductor light-emitting diode according to (6), wherein the total area of the surface ohmic electrodes is 5% or more and 30% or less of the total area of the open light emitting region. (8) The group III nitride crystal layer in contact with the surface ohmic electrode is formed of gallium phosphide (GaN _{1 - X} P _X , where 0
<III>, wherein the group III nitride semiconductor light emitting diode according to any one of (1) to (7),
It is.

Further, the present invention provides (9) a light emitting diode lamp using the group III nitride semiconductor light emitting diode according to any one of (1) to (8). (10) A light source using the light-emitting diode lamp according to (9). It is.

The present invention also provides (11) a gallium nitride (GaN) -based group III nitride crystal layer including a light-emitting portion having a heterojunction structure, and a conductive transparent oxide provided on the group III nitride crystal layer. An electrode used for a group III nitride semiconductor light-emitting diode having at least a window layer made of a crystal layer, wherein a surface formed between the surface of the group III nitride crystal layer and the window layer is electrically connected to the window layer. An III-nitride semiconductor light emitting diode, wherein an ohmic electrode is formed in contact with the surface of the III-nitride crystal layer, and a pedestal electrode for connection is formed at the center of the upper surface of the window layer. Electrodes. It is.

According to the present invention, (12) the electrode for a III-nitride semiconductor light emitting diode according to (11), wherein the surface ohmic electrode is arranged at a position around the pedestal electrode. (13) The electrode for a group III nitride semiconductor light emitting diode according to (11) or (12), wherein the surface ohmic electrode is disposed at a position symmetrical with respect to the center of the pedestal electrode. . (14) The electrode for a group III nitride semiconductor light-emitting diode according to any one of (11) to (13), wherein the surface ohmic electrode is provided at a position equidistant from the center of the pedestal electrode. (15) The surface ohmic electrode is composed of a plurality of electrodes arranged at equal intervals.
The electrode for a group III nitride semiconductor light-emitting diode according to any one of 1) to (14). (16) The surface ohmic electrode is arranged in a region other than the projection region of the pedestal electrode on the surface of the group III nitride crystal layer (hereinafter, referred to as an open emission region) (11) to (11). The electrode for a group III nitride semiconductor light-emitting diode according to (15). (17) The electrode for a group III nitride semiconductor light-emitting diode according to (16), wherein the total area of the surface ohmic electrodes is 5% or more and 30% or less of the total area of the open light emitting region. (18) the surface ohmic electrode in contact with the group III nitride crystal layer, to (11) do not, characterized in that it consists of gallium phosphide nitride (GaN _{1 over X} P _X, where 0 <X <1) (17 ) 3. The electrode for a group III nitride semiconductor light-emitting diode according to item 1. It is.

The present invention also provides (19) a first step of forming a surface ohmic electrode in contact with the surface of a gallium nitride (GaN) -based group III nitride crystal layer including a light emitting portion having a heterojunction structure; A second step of forming a window layer made of a conductive transparent oxide crystal layer which covers the surface of the group III nitride crystal layer and the surface ohmic electrode and is electrically connected to the surface ohmic electrode, following the step 1 And a third step of forming, in the center of the upper surface of the window layer, a pedestal electrode for connection with the window layer, the third step being subsequent to the second step. A method for manufacturing an electrode for a semiconductor light emitting diode. (20) A pedestal electrode is formed on a group III nitride crystal layer via a window layer made of a conductive transparent oxide crystal layer, and a conductive transparent oxide crystal layer is present on a surface where the pedestal electrode is connected. (19) The method for producing an electrode for a group III nitride semiconductor light-emitting diode according to (19). It is.

[0018]

FIG. 3 shows the above (1) or (1)
III representing the first embodiment according to the invention described in 1)
FIG. 3 is a schematic cross-sectional view for explaining the configuration of the group III nitride semiconductor LED 300 and its electrodes. The LED 300 according to the first embodiment includes a stacked structure 31 using a single crystal having conductivity as a substrate 301 as a base material. If a conductive single crystal is used as the substrate, an ohmic electrode of the first conductivity type can be provided as the back surface ohmic electrode 309 on the back surface of the substrate. That is, a conventional group III nitride LED using an electrically insulating single crystal such as sapphire as a substrate
Unlike the above, since the ohmic electrode is provided without dropping a part of the light emitting part, the reduction of the surface area of the light emitting part is avoided, and the group III nitride LED with high light emission intensity is provided.
To gain an advantage. In addition, if a single crystal having conductivity and cleavage properties is used as a substrate, it can be easily divided into individual elements by using cleavage of the crystal, and it is convenient to produce a group III nitride LED. Become. Silicon (Si), gallium phosphide (GaP), gallium arsenide (GaAs), and the like can be given as examples of single crystals that have both conductivity and cleavage and can be suitably used as a substrate. In addition, I
In view of the fact that the deposition temperature for laminating the group II nitride semiconductor layer is generally a high temperature exceeding about 800 ° C.,
Silicon single crystal (silicon) having heat resistance at high temperatures is suitably used as the substrate. For example, if the plane orientation is $ 10
P-type or n-type silicon with 0 or {111} is suitable as the substrate.

On the surface of a substrate 301 made of a conductive crystal,
Is a buffer layer 3 made of a boron phosphide (BP) -based material.
02 is provided. Boron phosphide (BP) based material
I containing at least boron (B) and phosphorus (P)
II-V compound semiconductor. Phosphorus as BP material
In addition to boron phosphide (BP), for example, boron nitride phosphide (BN
_1-XP_X: 0 <X <1) or boron / gallium phosphide (B_1-Y
Ga_YP: 0 <Y <1). BP material
Construct pn junction type double hetero (DH) light emitting unit 30
With group III nitride semiconductors such as gallium nitride (GaN)
Less lattice mismatch. example
For example, the nitrogen composition ratio (= 1−X) is set to 0.03 (3%).
BN_0.03P_0.97(Lattice constant = 4.510 °)
Of a buffer layer that achieves lattice matching with crystalline GaN
There is a point. That is, the buffer layer made of a BP-based material has a lattice alignment.
Crystal defect density such as misfit dislocation due to good compatibility
Demonstrates the effect of providing an upper layer with less crystallinity
You.

In the as-grown state, the BP-based buffer layer, which is mainly composed of an amorphous material, forms a lattice between the conductive single-crystal material forming the substrate and the constituent layers forming the laminated structure. This is particularly effective in reducing the inconsistency of This is because the crystal layer mainly composed of an amorphous body exhibits an effect of providing a high-quality upper layer because the crystal layer is crystallized while absorbing lattice distortion caused by lattice mismatch as the upper layer is formed. The BP-based buffer layer mainly composed of an amorphous material is, for example, a triethylboron ((C ₂ H ₅ ) ₃ B) / phosphine (PH ₃ ) reaction-based organometallic thermal decomposition, like the other constituent layers of the laminated structure. It is obtained by forming a film at a temperature higher than about 200 ° C. and lower than about 500 ° C. by a vapor phase epitaxy (MOCVD) method. Further, the film formation temperature is set to about 150 ° C. using a halogen vapor phase epitaxy (VPE) method of a boron trichloride (BCl ₃ ) / phosphorus trichloride (PCl ₃ ) reaction system.
It is obtained at a setting of about 750 ° C. Further, the film formation temperature is preferably in the range of about 200 ° C. or more and about 500 ° C. or less (see Japanese Patent Application Laid-Open No. 2000-58451). Regardless of the vapor phase growth means, the most important conditions for obtaining a BP-based buffer layer mainly composed of an amorphous body are:
This is the film forming temperature. If the film forming temperature is lower than about 200 ° C., the thermal decomposition of the raw material does not sufficiently proceed, so that there is a disadvantage that the buffer layer cannot be formed stably. On the other hand, when the growth temperature is 50
When the temperature exceeds 0 ° C., a polycrystalline layer is easily formed. On the polycrystalline layer in which the single crystals are randomly aggregated, the crystal easily grows in a random orientation, reflecting the orientation (coordination direction) of each single crystal constituting the polycrystalline layer. It is difficult to obtain an upper layer having a flat surface, which is inconvenient. Differences in the main constituent elements of the buffer layer can be known by analysis means such as general X-ray diffraction analysis and electron diffraction.

A low-temperature buffer layer formed of a BP-based material formed at a relatively low temperature in the range of 200 ° C. to 500 ° C., and a single-crystal layer formed of a BP-based material formed on the low-temperature buffer layer at a higher temperature. And may form a buffer layer. The BP-based crystal layer formed via the low-temperature buffer layer becomes a single crystal layer having a small crystal defect density and excellent crystallinity, and the single crystal layer is effective in obtaining an upper layer having a small defect density. That is,
A buffer layer composed of a plurality of layers of a BP-based low-temperature buffer layer and a BP-based high-temperature single-crystal layer thereon is effective in providing an upper layer having excellent crystallinity. As a configuration example of the corresponding buffer layer,
For example, a multilayer buffer layer composed of two layers of a low-temperature buffer layer made of amorphous boron phosphide (BP) and a BP single crystal layer can be exemplified. The high-temperature buffer layer is preferably formed at a temperature in the range of approximately 800 ° C. to 1200 ° C. using a vapor phase growth method such as the MOCVD method.

A light emitting section is formed on the low-temperature buffer layer or the multilayer buffer layer. The light emitting unit is a functional part that performs light emission, and includes at least a light emitting layer and a cladding layer. The light emitting section can be configured with either a single (single) heterostructure or a double (double) heterojunction structure. When the light-emitting portion is configured by a double hetero (DH) junction structure, it is superior in providing high-intensity light emission as compared with a single hetero junction structure due to the “confinement effect” of a carrier. FIG. 3 illustrates a light emitting section 30 having a pn junction DH structure including a light emitting layer 304 and a lower cladding layer 303 and an upper cladding layer 305 sandwiching the light emitting layer 304 as the first embodiment. Further, the intensity of the light emitted from the light emitting portion depends on the crystallinity of the functional layer constituting the light emitting portion, in particular, the crystal layer forming the light emitting layer. In general, the higher the quality of a crystal layer with less dislocations and defects, the higher the intensity of light emission. Therefore, it is preferable that the light emitting unit is formed of a crystal layer having a small lattice mismatch with the low-temperature buffer layer or the multilayer buffer layer. For example, if the gallium (Ga) composition ratio is 0.03
(3%) cubic boron gallium phosphide (B _0.97
Ga _0.03 P), cubic gallium nitride phosphide (GaN _0.97 P _0.03 ) having a phosphorus composition ratio of 0.03, and cubic gallium indium nitride (Ga _0.88 In _0.12 N having an indium composition ratio of 0.12) ) Is the same as the lattice constant of 4.56.
6 °. Than this, the B _0.97 Ga _{0. 03} P buffer layer, a GaN _0.97 P _0.03 and the cladding layer, Ga _0.88 an In
A light emitting portion of a lattice matching system can be formed using _0.12 N as a light emitting layer. That is, the light-emitting portion can be formed from a high-quality crystal layer having a small crystal defect density due to lattice mismatch.

The electrode on the front surface side of the group III nitride semiconductor LED 300 is formed on a surface of one of the constituent layers constituting the laminated structure 31, for example, the upper clad layer 305 constituting the light emitting portion 30 having the pn junction type DH structure. An ohmic electrode 308 is arranged, and the upper cladding layer 305 and the surface ohmic electrode 3
08 and a surface ohmic electrode 308
A window layer 306 made of a conductive transparent oxide crystal layer of ITO or the like provided so as to be electrically connected to the window layer 306 is overlaid, and a pedestal electrode 307 is provided at the center on the window layer 306. That is, the surface ohmic electrode 308 is formed separately from the pedestal electrode 307, and is not directly in contact with the pedestal electrode 307, but is formed as one constituent layer of the stacked structure 31 for the group III nitride semiconductor LED 300 (the LED 300 illustrated in FIG. 3). If there is upper cladding layer 3
05). Pedestal electrode 3
07 and the surface ohmic electrode 308 are electrically connected via a conductive transparent oxide crystal layer such as ITO forming the window layer 306. The window layer 306 has a transmittance that can efficiently emit light to the outside, and can be similarly formed of a transparent material other than ITO, which can supply an element operation current to the surface ohmic electrode 308. Examples of constituent materials other than ITO include zinc oxide (ZnO) and mixed oxides of zinc (Zn) and silicon (Si).

The electrode on the surface side of the LED 300 is formed on the surface of the upper cladding layer 305 in the first step by using a known technique such as photolithography.
08, and in the second step, a conductive transparent oxide that covers the surface of the upper cladding layer 305 and the surface ohmic electrode 308 and is electrically connected to the surface ohmic electrode 308 by using a method such as sputtering. A window layer 306 made of a crystal layer is formed, and subsequently, in a third step, a pedestal electrode 307 for connection is formed in the center of the upper surface of the window layer 306 for conduction with the window layer 306.

In this case, the pedestal electrode 307 is formed on the upper clad layer 305 with the window layer 30 made of a conductive transparent oxide crystal layer.
6, the conductive transparent oxide crystal layer does not exist on the surface of the pedestal electrode 307 where the connection is made. When the conductive transparent oxide crystal layer is present on the pedestal electrode 307, the region where the conductive transparent oxide crystal layer is located cannot be recognized because the transparent transparent oxide crystal layer is present, and connection is performed by wire bonding on the conductive transparent oxide crystal layer. As a result, a problem that the wire does not adhere to the pedestal electrode 307 may occur. On the other hand, the pedestal electrode 307 is formed on the conductive transparent oxide crystal layer, and the conductive transparent oxide crystal layer is not present on the surface where the pedestal electrode 307 is connected, so that this problem can be surely solved. Can be prevented.

In the present invention, in particular, the surface ohmic electrode 308 is arranged around the
It is characterized by constituting a group III nitride semiconductor LED. FIG.
An example of the arrangement of the surface ohmic electrode 308 according to the first embodiment will be described below. The surface ohmic electrode 308 disposed on the surface of the constituent layer 305 (see FIG. 3) of the laminated structure 31 (see FIG. 3) at a symmetrical position with respect to the pedestal electrode 307 is inside the constituent layer 305. In addition, it has the effect of distributing and diffusing the element operating current to the light emitting section 30 (see FIG. 3). Further, as a surface ohmic electrode having a configuration different from the plurality of surface ohmic electrodes 308 illustrated in FIG. 4, there is an example in which a single annular metal electrode is used. According to the present invention, an ohmic electrode is provided in the form of an island in an intermediate region between pedestal electrodes provided at the periphery of the light emitting element, not at the center of the light emitting element (Japanese Patent Laid-Open No. 57-11107).
Unlike the arrangement means as shown in the specification of Japanese Patent Application Laid-Open No. 6 (1999) -1995, a surface ohmic electrode is arranged around a pedestal electrode installed at the center of the light emitting element when viewed in plan.

Referring to FIG. 3, a pedestal electrode 30 will be described.
7 in a projection area 307a of the pedestal electrode 307 located below.
Light emitted from the light emitting unit 30 is applied to the pedestal electrode 307.
Can not be taken out efficiently because it is more shielded
No. That is, the projection is performed from the pedestal electrode 307 through the window layer 306.
The element operating current supplied to the region 307a is equal to the light emission intensity of the element.
Wasted without contributing efficiently to improve
Become. Therefore, in the second embodiment of the present invention, particularly,
The ohmic electrode 308 is connected to the laminated structure 31 III.
The projection region 307a of the pedestal electrode 307 of the group III nitride crystal layer
Table of outside area 307b (hereinafter, open emission area 307b)
Place on the surface. FIG. 4 shows a surface ohmic according to the present invention.
Schematic plan view of a group III nitride semiconductor LED provided with electrodes
Is shown. Surface ohmic disposed in open light emitting region 307b
The back-gate electrode 308 has an element operating voltage on the open light-emitting region 307b.
It exerts the effect of preferentially distributing and diffusing the flow. Also,
Emission is easily taken out because it is open to the outside
The device operating current is limited to the open light emitting region 307b to be
By allowing the light to flow inward, the open light emitting area 3
07b, for example, gallium indium nitride
(Ga _YIn_1-YN: 0 ≦ Y ≦ 1) as the light emitting layer 304
The current density of the element operating current flowing into the light emitting unit 30 provided is
Group III nitride semiconductor LE with increased emission intensity
This is effective in obtaining D.

Further, in the third embodiment of the present invention, the surface ohmic electrode is disposed on the surface of the open light emitting region at a position symmetrical with respect to the center of the pedestal electrode. The surface ohmic electrode arranged in a symmetrical positional relationship around the pedestal electrode exerts an action of uniformly diffusing the element operating current over a wide range of the light emitting portion. In particular, by arranging the surface ohmic electrode on the surface of the open light emitting region and symmetrically with respect to the center of the pedestal electrode, the current density of the element operating current flowing into the open light emitting region can be made uniform. Therefore, it is effective in obtaining a group III nitride semiconductor LED having uniform in-plane emission intensity.

Further, in the fourth embodiment of the present invention, the surface ohmic electrode is provided on the surface of the open light emitting region and at a position equidistant from the center of the pedestal electrode. The ohmic electrodes provided at equal intervals around the pedestal electrode exhibit an effect of uniformly and widely diffusing the element operating current in the light emitting portion. In particular, surface ohmic electrodes regularly arranged on the surface of the open light emitting region at the same distance from the pedestal electrode make the current density of the device operating current flowing into the open light emitting region uniform, and the open light emitting region This is effective in making the light emission intensity uniform in the device. As an example of the arrangement of the surface ohmic electrode according to the gist of the fourth embodiment, for example, a configuration is provided in which the surface ohmic electrode is provided at several positions on the circumference of a concentric circle centered on the center of the planar shape of the pedestal electrode. it can. It is not necessary that the planar shapes of the surface ohmic electrodes provided at several places are all the same, but it is desirable that the planar shapes of the surface ohmic electrodes located at least symmetrically with respect to the pedestal electrode be the same. This is because the potential distribution in the open light emitting region is made symmetrical to obtain light emission with a more uniform intensity than in the open light emitting region.

Further, in the fifth embodiment of the present invention, the surface ohmic electrode is composed of a plurality of electrodes arranged at equal intervals on the surface of one constituent layer of the laminated structure. By arranging a plurality of surface ohmic electrodes at equal intervals in the area around the pedestal electrode on the surface of one constituent layer, the element operating current supplied from the pedestal electrode via the window layer is evenly distributed to the light emitting portion A possible function is obtained. In particular, if the surface ohmic electrodes are provided at regular intervals on the surface of the open light emitting region without being in contact with the projection of the pedestal electrode, it is almost limited to the open light emitting region, that is, to the outside of the pedestal electrode other than the projected region. Since the element operating current can flow with high and uniform current density preferentially in a region where light can be easily extracted, it is advantageous for obtaining a group III nitride semiconductor LED with uniform in-plane emission intensity. Although the surface ohmic electrodes provided at equal intervals need not necessarily have the same planar shape, it is preferable to arrange surface ohmic electrodes having the same planar shape at symmetrical positions with respect to the pedestal electrode.

In particular, limited to the open light emitting region,
The surface ohmic electrode provided with the components shown in the fifth to fifth embodiments is most effective in flowing the element operating current preferentially and with a uniform current density in the open light emitting region. FIG. 5 is a schematic plan view illustrating one arrangement form of the surface ohmic electrode 508 having the contents described in the third to fifth embodiments comprehensively.
Specifically, (a) the pedestal electrode 5
Without contact with the projection area 07, the position symmetrical with respect to the base electrode 507 to the area around the pad electrode 507 in plan view, and the radius d ₁ around the center of (b) the base electrode 507 The pedestal electrode 50 is provided at several places on the circumferences 509 and 510 of two concentric circles having a radius d ₂ (where d ₂ > d ₁ ).
(C) having an electrode in which surface ohmic electrodes 508 are arranged at equal intervals on the same circumference (509 or 510) on the same circumference (509 or 510).
FIG. 1 is a schematic plan view of a group III nitride semiconductor LED. As shown in FIG. 5, by disposing the surface ohmic electrode 508 so as to equalize the current density of the device operating current flowing into the open light emitting region 507b, the element operating current is preferentially and evenly applied to the open light emitting region 507b. A group III nitride semiconductor LED that can be distributed and has no dimming at the periphery of the LED and has excellent in-plane uniformity of emission intensity is provided.

When the area where the surface ohmic electrode and the layered structure forming layer provided with the electrode are in contact with each other is reduced, the injection density (current density) of the device operating current is increased, and an improvement in emission intensity can be expected. On the other hand, when the contact area between the surface ohmic electrode and the constituent layer is reduced, the ohmic contact resistance is increased, and the forward voltage (forward voltage) is reduced.
stage: Vf) is disadvantageously increased. Thus, in the sixth embodiment of the present invention, the total area (= A) of the surface ohmic electrodes is determined by the total area (= A) of the open light emitting region.
30% at a ratio (= A / B) of 5% or more with respect to B)
It is specified below. Here, the total area of the open light emitting region (=
B) is an area given by subtracting the bottom area of the pedestal electrode corresponding to the surface area of the projection area of the pedestal electrode from the surface area of one constituent layer on which the surface ohmic electrode is arranged. Also,
The total area (= A) of the surface ohmic electrodes is the plane area of a single ohmic electrode, and refers to the total plane area of each ohmic electrode of a plurality of ohmic electrodes.

When the ratio of the total area (= A) of the surface ohmic electrodes to the total area (= B) of the open light-emitting region is less than 5%, the current density of the device operating current increases and the light emission intensity improves. However, when the forward current is set to 20 milliamperes (mA), Vf suddenly increases. For example, as compared to the group III nitride semiconductor LED in the preferred range, Vf is about 20% to 3%.
It increases by more than 0% and may be higher than 4.5 volts (V). On the other hand, as the area occupied by the surface ohmic electrode in the open light emitting region increases, Vf decreases. However, since the surface ohmic electrode is usually made of a metal that absorbs light emitted from the light emitting portion, the ratio (=
As the ratio A / B increases, the degree of absorption of light emission by the surface ohmic electrode made of metal also increases, and thus there is a disadvantage that the light emission intensity is significantly reduced. When the ratio of the total area (= A) of the surface ohmic electrodes to the total area (= B) of the open light-emitting region exceeds 30%, compared to the group III nitride semiconductor LED having the ratio in the preferable range, For example, the emission intensity of the LED at a forward current of 20 mA is about 4
It may decrease from 0% to about 50%.

For example, if an LED having a circular pedestal electrode having a diameter of 120 μm and having a side surface of 350 μm and a square surface is used, the projected area of the pedestal electrode can be calculated from the planar surface area of the LED. The total area of the open light-emitting region excluding becomes about 1.1 × 10 ⁻³ cm ² . The total area (= A) of the surface ohmic electrodes is 5.5 × 10 ⁻⁵ cm ² (A / B = 0.0) with respect to the total area (= B) of the open light emitting region.
5) At least 3.3 × 10 ⁻⁴ cm ² (A / B = 0.30)
By doing the following, a group III nitride semiconductor LED having high emission intensity and low forward voltage can be formed. For example, if a total of 12 circular surface ohmic electrodes having a diameter of 20 μm are arranged in an open light emitting region having a total area of about 1.1 × 10 ⁻³ cm ⁻² (= B), the area of the surface ohmic electrodes Is 9.4 × 10 ⁻⁶ cm ² ,
A group III nitride semiconductor LED having a ratio (A / B) of about 8.6% can be configured. The ratio (A / B) is usually adjusted by appropriately designing the diameter, width, or length of the surface ohmic electrode. However, when the ratio is particularly in the range of about 7% to about 10%, high emission intensity can be obtained. Keep and low Vf III
A group nitride semiconductor LED is conveniently provided. When the surface ohmic electrode is provided on the surface of the p-type group III nitride semiconductor layer, the ratio (= A / B) is set to n.
When it is larger than the case where it is provided on the surface of the group III nitride semiconductor layer, it is superior in making the current density of the device operating current flowing to the open light emitting region uniform. This is because the p-type group III nitride semiconductor has a lower carrier mobility than the n-type group III nitride semiconductor semiconductor, and thus the range in which the device operating current can be diffused is narrowed. This is because it is necessary to expand the contact area to expand the range in which the current spreads. In particular, in a p-side-up type LED in which a surface ohmic electrode is provided on the surface of a p-type group III nitride semiconductor layer, the ratio (= A
A good result can be obtained by setting / B) to be about 10% larger than the ratio (= A / B) which is suitable for the n-side up type LED.

A sudden increase in the forward voltage can be caused by one of the constituent layers (the contact (contac) where the surface ohmic electrode is provided).
t) It can be suppressed by reducing the contact resistance of the surface ohmic electrode depending on the material of the layer). Therefore, in the seventh embodiment of the present invention, the laminated structure constituting layer on which the surface ohmic electrode is arranged is formed of gallium nitride phosphide (GaN _{1 − X} P _X : 0 <X <
1) It is composed of a crystal layer. Conventionally, gallium nitride (GaN) has been frequently used as a contact layer (see Japanese Patent Application Laid-Open No. 6-268259). However, in the case of GaN _{1 − X} P _X (0 <X <1), the band gap can be changed by adjusting the phosphorus composition ratio (= X) (Ap
pl. Phys. Lett. , Vol. 60, no. 2
0 (1992), pp. 2540-2542). In other words, depending on the phosphorus composition ratio (= X), the contact layer can be formed from a group III nitride semiconductor material having a smaller band gap than gallium nitride (GaN). There is an advantage that a small surface ohmic electrode can be formed.

For example, the transition energy corresponding to blue light emission at a wavelength of 450 nanometers (nm) is about 2.75 eV. The transition energy corresponding to green light emission at a wavelength of 520 nm is about 2.38 eV. Thus, for an LED having a light emitting layer that provides blue emission, about 2.8 e
L having a light-emitting layer of at least V and emitting green light.
In the case of ED, G having a band gap of about 2.4 eV or more
When aN _{1 − X} P _X (0 <X <1) is used for the contact layer,
A contact layer in which absorption of light emission is suppressed can be formed. From the non-linear change of gallium phosphide gallium nitride (GaN _{1 − X} P _X : 0 <X <1), the above-mentioned Appl. Phys.
t. , Vol. 60, see FIG. 60), the contact layer having excellent transmittance for blue or green light emission is made of GaN _{1 - X} having a phosphorus composition ratio (= X) of 5% (X = 0.05) or less.
P _X (0 <X ≦ 0.05). Further, Ga having a phosphorus composition ratio (= X) of 5% (X = 0.05) or less is used.
To cross the room temperature band width at about 2.8eV of N _{1 over X P X (0 <X ≦} 0.05), also serves as a cladding layer or clad layer sandwiching the light emitting layer resulting in blue or green light There is an advantage that it can also be used as a contact layer.

The surface ohmic electrode provided on the surface of the contact layer composed of a gallium nitride (GaN) -based group III nitride crystal layer includes gold (Au), gold / germanium (Au · Ge), Gold and tin (Au ・ S
n) and the like. When the contact layer is p-type, indium-zinc (In-Zn), gold-
The surface ohmic electrode can be made of a zinc (Zn) -containing alloy such as zinc (Au.Zn) or a gold-beryllium (Au.Be) alloy. These metals are gallium nitride (GaN)
A good ohmic contact is formed with the group III nitride crystal layer. Especially when the contact layer is made of GaN _{1 over X} P _X,
These metals can form good ohmic contacts with low contact resistance. The pedestal electrode is preferably made of a metal having low electric resistance, such as gold (Au) or aluminum (Al).

[0038]

The surface ohmic electrode arranged around the pedestal electrode on the surface of the group III nitride semiconductor crystal layer of the present invention comprises:
It has the effect of diffusing the element operating current supplied from the pedestal electrode on the window layer through the window layer over a wide range of the light emitting section.

If the surface ohmic electrode is arranged in a region other than the projection region of the pedestal electrode (open light emitting region) on the surface of the group III nitride semiconductor crystal layer, priority is given to the open light emitting region where light emission can be easily taken out. Has the effect of causing the element operating current to flow therethrough.

The surface ohmic electrode disposed on the surface of the open light emitting region at a position symmetrical with respect to the center of the pedestal electrode has a function of preferentially and uniformly diffusing the element operating current into the open light emitting region.

The surface ohmic electrode provided at a position equidistant from the center of the pedestal electrode on the surface of the open light emitting region has the function of making the element operating current flowing into the open light emitting region more uniform.

The surface ohmic electrode composed of a plurality of electrodes arranged at equal intervals has an effect of equalizing the current density of the device operating current flowing into the open light emitting region.

When the total area of the surface ohmic electrodes is controlled to 5% or more and 30% or less of the total area of the open light-emitting region, there is an effect of improving the light emission intensity without increasing the forward voltage. .

Gallium phosphide nitride (GaN _{1 - X} P _X : 0 <
X <1) When the crystal layer is used as the contact layer of the surface ohmic electrode, it has an effect of providing a surface ohmic electrode with low contact resistance.

[0045]

(Example 1) Hereinafter, a group III nitride semiconductor light-emitting diode and its electrode according to the present invention will be described in detail based on examples. FIG. 6 is a diagram illustrating a III according to the first embodiment.
1 is a schematic plan view of a group III nitride semiconductor LED 600. FIG. FIG. 7 is a schematic cross-sectional view of the LED 600 shown in FIG. 6 along the broken line AA ′.

The LED 600 has the following layers 6 on a substrate 601.
It was configured based on the laminated structure 61 provided with 02 to 605. (1) Boron (B) doped p-type conductive (100)
Substrate 601 made of Si single crystal having surface (2) Triethyl borane ((C ₂ H ₅ ) ₃ B) / phosphine (PH ₃ ) / hydrogen (H ₂ ) reaction system at normal pressure (atmospheric pressure) MO
At 350 ° C., PH ₃ and (C
_A layer thickness of about 20 nanometers (nm) was grown by setting the supply ratio (V / III ratio) of ₂ H ₅ ) ₃ B to about 300.
Low-temperature buffer layer 602 made of Zn-doped p-type boron phosphide (BP) (3) Atmospheric pressure MOCVD of a reaction system of trimethylgallium ((CH ₃ ) ₃ Ga) / ammonia (NH ₃ ) / PH ₃ / H ₂ By using dimethylzinc ((CH ₃ ) ₂ Zn) as a Zn doping raw material, the layer was laminated at about 1000 ° C. on the p-type BP low-temperature buffer layer 602, the layer thickness was about 0.8 μm, and the carrier concentration was about Zn-doped p at 1 × 10 ¹⁸ cm ^-3
-Type boron phosphide (BP) single crystal layer 603 (4) (CH ₃ ) ₃ Ga / trimethylindium ((CH
₃ ) Average indium (I) grown at 880 ° C. by atmospheric pressure MOCVD using a ₃ In) / NH ₃ / H ₂ reaction system.
n) An n-type gallium nitride-indium mixed crystal (approximately 0.06 (6%)) composed of a multiphase structure composed of a plurality of phases having different In compositions and having a layer thickness of about 8 nm ( Light emitting layer 604 made of Ga _0.94 In _0.06 N) (5) Normal pressure MOC of (CH ₃ ) ₃ Ga / NH ₃ / H ₂ reaction system
The layer thickness grown at 1080 ° C. by the VD method is about 0.1
μm and a carrier concentration of about 2 × 10 ¹⁸ cm ⁻³
Gallium nitride (GaN) layer 605

Pn junction type double hetero (DH) junction structure
The light emitting part 60 of the above is laminated on the low temperature buffer layer 602.
The p-type BP single crystal layer 603 is used as a lower cladding layer, and Ga
_0.94In _0.06The N layer 604 is used as a light emitting layer, and n-type Ga
The N layer 605 was configured as an upper cladding layer. Upper class
Projected area 60 of pedestal electrode 607 on the surface of pad layer 605
The open light emitting area 607b other than 7a is made of gold (Au).
N-type surface ohmic electrodes 609
Was. The n-type surface ohmic electrode 609 is
The entire surface of the layer 605 is once coated with a vacuum deposited film of gold (Au).
After coating, known photolithography (photolithography)
Through patterning means utilizing technology,
It was formed by a technique of leaving the Au vapor-deposited film only in the region.
The Au deposited film covering the area other than the desired area is wet-etched.
And removed with a cleaning solution. After that, the upper cladding layer 605
Leaving an n-type surface ohmic electrode 609 on the surface of
In an acid state using a normal high-frequency sputtering method.
Window layer 6 made of indium tin oxide / tin oxide (ITO)
06 was deposited. Resistivity of ITO film forming window layer 606
Is about 6 × 10^-FourIn ohm centimeters (Ω · cm)
The thickness was about 550 nanometers (nm).

In addition to the surface ohmic electrode 609, the following electrodes were formed on the laminated structure 61 by using a known photolithography technique or the like to constitute an LED 600. (1) A circular pedestal electrode 607 having a diameter of 120 μm and made of gold (Au) formed at the center of the window layer 606 (2) Aluminum (Al) formed on substantially the entire back surface of the Si single crystal substrate 601 P-type back ohmic electrode 608

The n-type surface ohmic electrode 609 is formed by arranging metal electrodes made of the same circular Au having a diameter of 30 μm at a total of eight locations on the surface of the open light emitting region 607b. The total area (= A) of the n-type surface ohmic electrodes 609 was about 5.6 × 10 ⁻⁵ cm ² . The surface ohmic electrode 609 has a central angle of 45 at a position on a circumference having a radius of 120 μm around the center of the pedestal electrode 607.
° and distributed at equal intervals of about 46 µm in a linear distance from each other. After that, the Si single crystal substrate 601
Of the electrodes 607 to 6 using the cleavage in the [110] direction.
The laminated structure 60 on which 09 was formed was divided into individual elements (chips) 600 by a general scribing means. The planar shape of the chip 600 is a square having one side of about 350 μm, the diameter of the pedestal electrode 607 is 120 μm as described above, and the area (= B) of the open light emitting region 607b is about 1.1 ×
It was set to 10 ⁻³ cm ² . Therefore, the ratio of the total area of the surface ohmic electrodes to the total area of the open light emitting region 607b (= A / B) was about 5.1%.

The front ohmic electrode 609 and the rear ohmic electrode 608 via the pedestal electrode 607 and the window layer 606
During this time, an operating current was passed to obtain the following emission characteristics. (A) Emission wavelength = 440 nm (b) Emission luminance = 1.6 candela (cd) (however, forward current = 20 mA) (c) Forward voltage = 3.8 volts (V) (however, forward current = (D) Reverse voltage = 20 V or more (however, reverse current = 1
0 μA) According to the configuration of the surface ohmic electrode as in this embodiment,
Since a device operating current can be preferentially passed through the open light emitting region conveniently, a group III nitride semiconductor light emitting device having particularly high light emission intensity has been provided.

(Embodiment 2) In the present embodiment 2, the same layered structure 61 as that described in the embodiment 1 is used, and the group III having the surface ohmic electrode 609 arranged differently from the embodiment 1 is used. The present invention will be described using an example in which a nitride semiconductor light emitting diode 700 is manufactured.

FIG. 8 is a schematic plan view of a group III nitride semiconductor LED 700 according to the second embodiment. In FIG. 8, the same portions as those described in FIG.
The same reference numerals are given and the description is omitted.

Example 3 Group III Nitride Semiconductor LED
In 700, the open light emitting region 60 around the pedestal electrode 607
7b, a frame-shaped surface ohmic electrode 609 having a multilayer structure in which the lower layer is made of gold (Au) and the upper layer is made of nickel oxide (NiO _x : X is approximately 1) is provided. The outer edge of the frame-shaped surface ohmic electrode 609 has a square shape reflecting the outer shape of the square LED 700 having a side of 320 μm,
The inner edge has a circular shape similar to the circular pedestal electrode 607 having a diameter of 120 μm. Center 607c of pedestal electrode 607
The distance from to the outer edge of the frame-shaped surface ohmic electrode 609 was set to 120 μm, and the distance to the inner edge of the circle was set to 100 μm in radius from the center 607c. In other words, a planar surface ohmic electrode 609 obtained by hollowing out a circular region having a diameter of 200 μm from the center of a square having a side of 240 μm is formed at the center 607 c of the pedestal electrode 607.
Are arranged symmetrically with respect to any of the center line C and the diagonal line D passing through. Ratio of area of surface ohmic electrode 609 to total area of open light emitting region 607b (= A / B)
Was about 28.8%.

After the surface ohmic electrode 609 is formed by using ordinary vacuum evaporation means and photolithography (photo etching) means, the same ITO film as in Example 1 is used as the window layer 606 by a general high frequency sputtering method. Deposited. A pedestal electrode 607 made of gold (Au) was provided at the center of the window layer 606. After a back surface ohmic electrode 608 made of aluminum (Al) was formed on the back surface of the Si single crystal substrate 601, the LED 700 was divided by scribing means using cleavage.

The characteristics of the LED 700 when an operating current was passed between the pedestal electrode 607 and the back ohmic electrode 608 were as follows. (B) Emission wavelength = 440 nm (b) Emission luminance = 1.4 candela (cd) (however, forward current = 20 mA) (c) Forward voltage = 3.6 volts (V) (however, forward current = (D) Reverse voltage = 20 V or more (however, reverse current = 1
0 μA) As described above, in Example 2, a group III nitride semiconductor light-emitting diode having a low forward voltage and a high luminous intensity was obtained. In addition, a near field (near f) acquired to verify the uniformity of the relative intensity of light emission in the open light emitting region.
According to the pattern (ield), it was recognized that the light emission intensity was uniform over substantially the entire surface of the open light-emitting region. This indicates that, by forming the surface ohmic electrode from the electrodes distributed to the open light emitting region, the element operating current can flow evenly over substantially the entire open light emitting region.

Next, the group III nitride semiconductor LED 7
A light emitting diode (LED) lamp manufactured by using No. 00 will be described. FIG. 10 is a diagram showing a configuration of an LED lamp manufactured using this LED. In the figure, L
The ED lamp 80 includes a light-emitting diode 81, a mount lead 82, and an inner lead 83, and is formed by molding the whole of these with a transparent resin 84.

As the light emitting diode 81, the group III nitride semiconductor LED 700 manufactured in the second embodiment is used, and the electrode 81 formed on the back surface of the substrate of the light emitting diode 81 is used.
a (the back ohmic electrode 608 of the LED 700) is fixed on the mount lead 82 so as to make electrical contact with the mount lead 82, and the pedestal electrode 81b of the light emitting diode 81 (the pedestal electrode 607 of the LED 700) is wire-bonded. It is connected to the inner lead 83.

This LED lamp 80 is the same as the LED lamp of the present invention.
Since the group nitride semiconductor light emitting diode is used, the luminous efficiency is improved as compared with the conventional one using the LED. Further, the LED lamp 80 includes a vehicle lamp, a railway vehicle lamp, a traffic signal light, a railroad crossing signal light,
Roadside indicator light, gaze guidance light, or monitor indicator,
The LED lamp 8 can be used as a light source for an operation panel display, as a light source for office equipment such as a copier and a facsimile, and an information board used outdoors.
A light source using 0 has higher luminous efficiency than a conventional light source.

(Embodiment 3) In this embodiment 3, on the n-type gallium nitride (GaN) layer 605, which is the outermost layer of the laminated structure described in the embodiment 1, a phosphide nitride is further formed as an ohmic contact layer 610. Gallium (GaN _{1 - X} P _X , where X = 0.03) is laminated using a laminated structure.
A group II nitride semiconductor LED was constructed. FIG. 9 shows a schematic cross-sectional view of the group III nitride semiconductor LED according to the third embodiment. In FIG. 9, the same components as those shown in FIG. 7 are denoted by the same reference numerals, and description thereof will be omitted.

An n-type gallium nitride phosphide (GaN) having a phosphorus composition ratio of 3% forming ohmic contact layer 610
_0.97 P _0.03 ) is trimethylgallium ((CH ₃ ) ₃ G
a) / ammonia (NH ₃ ) / phosphine (PH ₃ ) / hydrogen (H ₂ ) at 980 ° C. by a reduced pressure MOCVD method.
Grew up. The carrier concentration of the ohmic contact layer 610 was adjusted to about 2 × 10 ¹⁸ cm ⁻³ by using disilane (Si ₂ H ₆ ) as an n-type doping gas. The thickness of the ohmic contact layer 610 was about 0.15 μm.

A surface ohmic electrode 609 made of gold (Au) having the same outer shape and bottom area as in Example 2 was formed on the open light emitting region 607b on the surface of the n-type GaN _0.97 P _0.03 ohmic contact layer 610. . Thereafter, as described in Example 2, the surface ohmic electrode 609 is coated with an ITO film forming the window layer 606, and the lower layer is made of chromium (Cr) and the upper layer is made of gold (Au) at the center of the ITO window layer. A circular pedestal electrode 60 having a diameter of 120 μm.
7 was installed. A back surface ohmic electrode 608 made of aluminum (Al) was provided on substantially the entire back surface of the p-type Si single crystal substrate 601 to constitute a group III nitride semiconductor LED.

The main characteristics of the group III nitride semiconductor LED of Example 3 formed by providing the surface ohmic electrode 609 on the open light emitting region 607b on the surface of the n-type GaN _0.97 P _0.03 ohmic contact layer 610 are summarized below. (A) Emission wavelength = 440 nm (B) Emission luminance = 1.3 candela (cd) (However, forward current = 20 mA) (C) Forward voltage = 3.2 volts (V) (However, forward current = (D) Reverse voltage = 20 V or more (however, reverse current = 1
0 μA) The group III nitride semiconductor LED obtained in Example 3 is:
Compared with the group III nitride semiconductor LED obtained in Example 2, although there is no difference in emission wavelength and reverse voltage, the GaN _0.97 P _0.03 layer is used as the ohmic contact layer, so that the emission intensity is high. While demonstrating
As a result, the effect of reducing the forward voltage was obtained.

[0063]

According to the present invention, since the element operating current can be passed through the light emitting portion on average, there is an effect that a group III nitride semiconductor LED having high light emission intensity can be provided. In particular, in the present invention, a surface ohmic electrode is arranged on the surface of the open light-emitting region other than the projection region of the pedestal electrode,
(1) The surface ohmic electrodes are arranged at symmetrical positions with respect to the center of the pedestal electrode, (2) The surface ohmic electrodes are arranged at the same distance from the center of the pedestal electrode, and (3) The surface ohmic electrodes are arranged at equal intervals to each other. When a configuration such as disposition is adopted, the element operating current can flow through the open light emitting region preferentially and uniformly, so that the current density of the element operating current that can flow through the open light emitting region can be increased. This is effective in obtaining a group III nitride semiconductor LED.

In the present invention, when the total plane area of the surface ohmic electrodes laid in the open light emitting region is controlled to be 5% or more and 30% or less of the total surface area of the open light emitting region, high light emission intensity can be maintained. There is an effect that a group III nitride semiconductor LED having a low forward voltage is provided. Further, in the present invention, when the surface ohmic electrode is provided on the surface of the gallium nitride phosphide (GaN _{1 − X} P _X : 0 <X <1) crystal layer, the group III nitride semiconductor LED with further reduced forward voltage Can be provided.

The group III nitride semiconductor light emitting diode electrode used in the above group III nitride semiconductor light emitting diode of the present invention can provide an LED having a high light emission intensity. Further, according to the method for producing an electrode for a group III nitride semiconductor light emitting diode of the present invention, an electrode used for producing a group III nitride semiconductor LED having high emission intensity can be produced with a high yield. In particular, a pedestal electrode is formed on the conductive transparent oxide crystal layer, and the conductive transparent oxide crystal layer does not exist on the surface where the pedestal electrode is connected, so that the connection by wire bonding can be made conductive transparent. It is possible to reliably prevent a defect that the wire is not adhered to the pedestal electrode 307 due to the operation on the oxide crystal layer.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a conventional group III nitride semiconductor LED.

FIG. 2 is a schematic plan view of a conventional group III nitride semiconductor LED.

FIG. 3 shows an I with a surface ohmic electrode according to the invention.
It is a cross section of a II nitride semiconductor LED.

FIG. 4 shows an I with a surface ohmic electrode according to the invention.
It is a plane schematic diagram of a group II nitride semiconductor LED.

FIG. 5 is a schematic plan view of another group III nitride semiconductor LED including a surface ohmic electrode according to the present invention.

FIG. 6 is a schematic plan view of a group III nitride semiconductor LED according to Example 1 of the present invention.

FIG. 7 is a schematic cross-sectional view of the LED shown in FIG. 6 taken along a broken line AA ′.

FIG. 8 is a schematic plan view of a group III nitride semiconductor LED according to a second embodiment of the present invention.

FIG. 9 is a schematic sectional view of a group III nitride semiconductor LED according to a third embodiment of the present invention.

FIG. 10 is a diagram showing a configuration of a light emitting diode lamp of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Light-emitting part 100 Group III nitride semiconductor LED 101 Sapphire substrate 102 Buffer layer 103 Lower cladding layer 104 Light emitting layer 105 Upper cladding layer 106 P-type ohmic electrode 107 N-type ohmic electrode 200 Group III nitride semiconductor LED 201 Surface ohmic electrode 202 Stack One constituent layer of the structure 30 Light emitting unit 31 Stacked structure 300 Group III nitride semiconductor LED 301 Substrate 302 Buffer layer 303 Lower cladding layer 304 Light emitting layer 305 Upper cladding layer 306 Window layer 307 Pedestal electrode 307a Projection area of pedestal electrode 307b Open circumference 510 radius of a circle the center 508 surface ohmic electrode 509 radius of the light emitting region 308 surface ohmic electrode 309 backside ohmic electrode 507 pad electrode 507b open-emitting region 507c pad electrode and d ₁ circumferential d ₁ seat electrode radius d ₂ radius 60 light emitting portion 61 laminated structure 600 III group centered on the center of the pad electrode nitride semiconductor LED 601 substrate 602 low-temperature buffer layer around the center of the circle d ₂ 603 p-type BP single crystal layer (lower cladding layer) 604 light-emitting layer 605 n-type GaN layer (upper cladding layer) 606 window layer 607 pedestal electrode 607a projection area of pedestal electrode 607b open emission area 607c center of pedestal electrode 608 back ohmic electrode 609 Surface ohmic electrode 610 Ohmic contact layer 700 Group III nitride semiconductor LED 80 LED lamp 81 Light emitting diode 81a Electrode formed on backside of substrate 81b Pedestal electrode 82 Mount lead 83 Inner lead 84 Resin C Center of LED passing through center of pedestal electrode Line D Center of the pedestal electrode Diagonal line of LED passing

Claims (20)

[Claims] 1. A first conductivity type single crystal substrate having a first conductivity type back ohmic electrode on a back surface, and a buffer made of a boron phosphide (BP) material formed on the surface of the single crystal substrate. Layer, a gallium nitride (GaN) -based group III nitride crystal layer including a light emitting portion having a hetero junction structure provided on the buffer layer, and a conductive transparent oxide provided on the group III nitride crystal layer II having at least a window layer made of a material crystal layer
In the group I nitride semiconductor light-emitting diode, said III
A second conductive type surface ohmic electrode which is electrically connected to the window layer between the surface of the group III nitride crystal layer and the window layer;
A group III nitride semiconductor light-emitting diode, formed in contact with the surface of a group II nitride crystal layer, and having a pedestal electrode for connection formed at the center of the upper surface of the window layer. 2. The group III nitride semiconductor light emitting diode according to claim 1, wherein said surface ohmic electrode is disposed around said pedestal electrode. 3. The group III nitride semiconductor light emitting diode according to claim 1, wherein the surface ohmic electrode is disposed at a position symmetrical with respect to the center of the pedestal electrode. 4. The group III nitride semiconductor light emitting diode according to claim 1, wherein said surface ohmic electrode is provided at a position equidistant from a center of said pedestal electrode. 5. The group III nitride semiconductor light emitting diode according to claim 1, wherein said surface ohmic electrode comprises a plurality of electrodes arranged at equal intervals. 6. The semiconductor device according to claim 1, wherein the surface ohmic electrode is arranged in a region other than a projection region of the pedestal electrode on the surface of the group III nitride crystal layer (hereinafter, referred to as an open light emitting region). 6. The group III nitride semiconductor light emitting diode according to any one of 1 to 5. 7. The total of the area of the surface ohmic electrode is:
7. The group III nitride semiconductor light emitting diode according to claim 6, wherein the total area of the open light emitting region is 5% or more and 30% or less. 8. A group III nitride crystal layer in contact with said surface ohmic electrode is formed of gallium nitride phosphide (GaN _{1 - X} P _X ,
8. The group III nitride semiconductor light emitting diode according to claim 1, wherein 0 <X <1). 9. A light emitting diode lamp using the group III nitride semiconductor light emitting diode according to claim 1. 10. A light source using the light-emitting diode lamp according to claim 9. 11. A window layer comprising a gallium nitride (GaN) group III nitride crystal layer including a light emitting portion having a heterojunction structure, and a conductive transparent oxide crystal layer provided on the group III nitride crystal layer. An electrode used in a group III nitride semiconductor light emitting diode comprising at least
A surface ohmic electrode that conducts with the window layer is formed between the surface of the group III nitride crystal layer and the window layer in contact with the surface of the group III nitride crystal layer. An electrode for a group III nitride semiconductor light emitting diode, wherein a pedestal electrode for connection is formed at the center. 12. The group III nitride semiconductor light emitting diode electrode according to claim 11, wherein said surface ohmic electrode is arranged at a position around said pedestal electrode. 13. The group III nitride semiconductor light emitting diode electrode according to claim 11, wherein said surface ohmic electrode is disposed at a position symmetrical with respect to the center of said pedestal electrode. . 14. The group III nitride semiconductor light emitting diode electrode according to claim 11, wherein said surface ohmic electrode is provided at a position equidistant from the center of said pedestal electrode. 15. The electrode for a group III nitride semiconductor light emitting diode according to claim 11, wherein said surface ohmic electrode comprises a plurality of electrodes arranged at equal intervals. 16. The method according to claim 16, wherein the surface ohmic electrode comprises the III.
The group III nitride semiconductor light-emitting diode according to claim 11, wherein the group III nitride semiconductor light-emitting diode is disposed in a region other than a projection region of the pedestal electrode on a surface of the group nitride crystal layer (hereinafter, referred to as an open light-emitting region). Electrodes. 17. The group III nitride semiconductor light emitting diode according to claim 16, wherein the total area of the surface ohmic electrodes is not less than 5% and not more than 30% of the total area of the open light emitting region. electrode. 18. A III in contact with said surface ohmic electrode
Gallium nitride phosphide (GaN)
_-1-X P _X, where 0 <X <1 claims 11, characterized in that it consists of) to the Group III nitride semiconductor light emitting diode electrode according to 17. 19. A first step of forming a surface ohmic electrode in contact with a surface of a gallium nitride (GaN) -based group III nitride crystal layer including a light-emitting portion having a heterojunction structure;
A second step of forming a window layer made of a conductive transparent oxide crystal layer that covers the surface of the group III nitride crystal layer and the surface ohmic electrode and is electrically connected to the surface ohmic electrode; A third step of forming a pedestal electrode for connection in the center of the upper surface of the window layer, which is electrically connected to the window layer, following the second step. A method for manufacturing a diode electrode. 20. A pedestal electrode is formed on a group III nitride crystal layer via a window layer made of a conductive transparent oxide crystal layer,
20. The method for manufacturing an electrode for a group III nitride semiconductor light emitting diode according to claim 19, wherein the conductive transparent oxide crystal layer is not present on the surface where the pedestal electrode is connected.