JP2003101071A - Semiconductor light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-luminance semiconductor light-emitting device having a small forward voltage, without the problems of peeling in a surface electrode due to dicing, wire bonding, or the like. SOLUTION: In the semiconductor light-emitting device, an emission section layer 12, made of an active layer 3, is sandwiched by a pair of clad layers 2 and 4, a transparent conductive layer 7 made of a metal oxide film, and a surface electrode 9 are formed on a first conductivity substrate 1 where a back surface electrode 10 is formed. In the semiconductor light-emitting device, the transparent conductive layer 7 has at least one through-hole 11, a layer 13 made of at least one type of metals selected from Ti, Zr, Mo, Ta, W, Pt, Ir, Os, Re, Rh, and Pd and a group made of their alloy is formed in the through- hole 11, or in the through-hole 11 or its peripheral section, and the surface electrode 9 is in contact with the emission section layer 12 via the metal layer 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-brightness semiconductor light-emitting device having a low forward operating voltage and excellent dispersibility of current flowing from a surface electrode to a semiconductor layer without peeling of the surface electrode during dicing or wire bonding. Regarding

[0002]

2. Description of the Related Art As a conventional light emitting diode (LED), G
Most were aP green LEDs and AlGaAs red LEDs. However, recently GaN and AlGaInP
A technique for growing a crystal layer of a system by a metal organic vapor phase epitaxy (MOVPE) has been developed, and it has become possible to manufacture an orange, yellow, green, and blue high-intensity light emitting diode.

By using an epitaxial wafer formed by the MOVPE method, it is possible to manufacture an LED that can obtain light emission of short wavelength and high brightness, which have been impossible up to now. Figure 7 shows the conventional L
An example of the cross-sectional structure of the ED is shown. This LED has a light emitting part layer 12 of a double hetero structure composed of an n-type AlGaInP clad layer 2, an undoped AlGaInP active layer 3 and a p-type AlGaInP clad layer 4 on the first main surface of an n-type GaAs substrate 1. Furthermore p
A current spreading layer 5 made of p-type GaP or the like is formed on the mold cladding layer 4, and a transparent conductive layer 7 is formed thereon. A surface electrode 9 made of Au or the like is provided on a part of the surface of the transparent conductive layer 7.
(Light extraction side) is formed, and an electrode 10 (back surface electrode) made entirely of AuGe alloy or the like is formed on the second main surface (back surface) of the substrate 1.

A metal oxide such as indium tin oxide (ITO) is known as a material for the transparent conductive layer which has sufficient translucency and conductivity required for obtaining sufficient current distribution. When an ITO film is used as a transparent conductive layer, the conventional thick current distribution layer is not required, so a low-cost and high-brightness LE
You can get D. An example of an LED in which an ITO film is provided between the surface electrode on the light extraction side and the light emitting layer is described in US Pat.
No. 1,122, JP-A No. 11-4020 and the like.

However, in an LED in which a surface electrode is formed on an epitaxial wafer via a metal oxide layer such as an ITO film, there is a problem that the surface electrode is peeled off in a process such as dicing or wire bonding. Do you get it. In addition, contact resistance occurs between the transparent conductive layer and the metal electrode,
There is also a problem that the forward operating voltage becomes high. Therefore, it is difficult to put the LED having the surface electrode formed on the epitaxial wafer via the ITO film into practical use.

As a result of earnest research in view of the above problems, through holes are formed in the transparent conductive layer formed on the light emitting portion layer (on the current diffusion layer and / or the compound semiconductor layer, if any). By providing the surface electrode so as to contact the exposed light emitting part layer, the current spreading layer or the compound semiconductor layer, the existing wire bonder can easily bond while preventing the surface electrode from peeling, and the forward operating voltage It turned out to drop. FIG. 6 shows an example of such a semiconductor light emitting device. The current distribution layer 5 is the same as in FIG. 7, and the surface electrode 9 is in direct contact with the current distribution layer 5 through the through hole 11 provided in the transparent conductive layer 7.

In a semiconductor light emitting device having a structure in which a surface electrode is vapor-deposited on a transparent conductive layer having a through hole, the problem of peeling of the surface electrode is substantially solved, but a semiconductor (a current spreading layer, etc.) in direct contact with the surface electrode is solved. It was found that there is a tendency that a large amount of current flows in the), and the current dispersion effect decreases. If a large amount of light is emitted from the light emitting layer directly below the surface electrode, the emitted light cannot be efficiently extracted to the outside. Therefore, in the semiconductor light emitting device having a structure in which the surface electrode is directly contacted with the semiconductor layer through the through hole of the transparent conductive layer to prevent the surface electrode from peeling, it is desired to improve the current dispersion property.

Therefore, an object of the present invention is a semiconductor light emitting device having a high forward luminance and having no problem of peeling of a surface electrode due to dicing or wire bonding, and having a low forward operation voltage. It is an object of the present invention to provide a semiconductor light emitting device that suppresses an excessive increase in light emission immediately below an electrode.

[0009]

As a result of earnest research in view of the above object, the present inventors have found that (a) a through hole is formed in a transparent conductive layer and an exposed semiconductor layer (a light emitting layer, a current spreading layer or By providing the surface electrode so as to contact the compound semiconductor layer), the existing wire bonder can be easily bonded while preventing the surface electrode from peeling, and the forward operating voltage is reduced, and (b ) By bringing the surface electrode into contact with the semiconductor layer through a layer made of a predetermined metal formed in the through hole, current dispersibility is improved, and excessive increase in light emission immediately below the surface electrode is suppressed. After discovering this, the present invention was conceived.

That is, in the semiconductor light emitting device of the present invention, a light emitting portion layer made of an active layer sandwiched between a pair of clad layers and a transparent metal oxide film are formed on a substrate of the first conductivity type having a back electrode formed thereon. A conductive layer and a surface electrode are formed, and the transparent conductive layer has at least one through hole,
Ti, Zr, Mo, Ta, W, Pt, Ir, Os, Re, R in the through holes
A layer made of at least one metal selected from the group consisting of h, Pd and alloys thereof is formed, and the surface electrode is in contact with the light emitting section layer through the metal layer. To do. A layer made of the same metal may be formed on the transparent conductive layer around the through hole in a region in contact with the surface electrode. The metal layer is preferably made of Ti or its alloy.

In one embodiment of the present invention, a second conductive type current spreading layer is formed between the light emitting layer and the transparent conductive layer, and the surface electrode is formed in the through hole. It is in contact with the current spreading layer via the metal layer.

In another embodiment of the present invention, a compound semiconductor layer is formed between the light emitting section layer and the transparent conductive layer, and the surface electrode has a metal layer formed in the through hole. Is in contact with the compound semiconductor layer.

In still another embodiment of the present invention, a compound semiconductor layer is formed between the current spreading layer and the transparent conductive layer, and the surface electrode is a metal layer formed in the through hole. It is in contact with the compound semiconductor layer through.

It is preferable that the light emitting portion layer comprises a first conductivity type clad layer, a second conductivity type clad layer, and an active layer sandwiched between the both clad layers.

The area of the through-hole (total area when there are a plurality of through-holes) is preferably 1% or more of the area of the surface electrode. In addition, it is preferable that the center of the region of the light emitting portion layer, the current spreading layer, or the compound semiconductor layer that is in contact with the surface electrode substantially coincide with the center of the surface electrode.

The substrate is made of GaAs, and the light emitting layer is
It is preferably composed of AlGaInP or GaInP. The current spreading layer is GaP, GaAlP, AlInP, AlGaInP, AlGaAs and GaAs.
It is preferably composed of at least one compound semiconductor selected from the group consisting of P.

The compound semiconductor layer comprises (1) InP or InAs
Binary compound semiconductor of (2) AlInAs or AlInP ternary compound semiconductor, (3) AlGaAs, AlGaP, GaInAs, and GaInP, at least one ternary compound semiconductor (mol of Ga (Ratio: 0.2 or less), (4) AlInAsP quaternary compound semiconductor, (5) AlGaInP, AlGaInAs, AlGaAsP and GaIn
At least one quaternary compound semiconductor (molar ratio of Ga: 0.2 or less) selected from the group consisting of AsP, or (6) AlGaInA
It is preferably any of quinary compound semiconductors composed of sP (molar ratio of Ga: 0.2 or less).

The metal oxide forming the transparent conductive layer is Sn
It is preferably at least one selected from the group consisting of O ₂ , In ₂ O ₃ , ITO and Ga-containing ZnO.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION [1] Semiconductor Light-Emitting Element (A) Layer Structure A semiconductor light-emitting element (for example, a light-emitting diode) of the present invention is
A through hole is formed in a transparent conductive layer formed on an epitaxial wafer, and a surface electrode is provided so as to be in contact with the exposed semiconductor layer (light emitting portion layer, current spreading layer or compound semiconductor layer) via a predetermined metal layer. It is characterized by Hereinafter, the structure of the semiconductor light emitting device of the present invention will be described in detail with reference to the drawings.

(1) First Embodiment FIG. 1 is a vertical sectional view of a semiconductor light emitting device according to a first embodiment of the present invention, FIG. 2 is a plan view thereof, and FIG.
Corresponds to A vertical section. An n-type AlGaInP clad layer 2 is formed on the first major surface of the n-type GaAs substrate 1, an undoped AlGaInP active layer 3 is formed on the clad layer 2, and an active layer 3 is formed.
A p-type AlGaInP clad layer 4 is formed on the above, and the n-type clad layer 2, the active layer 3 and the p-type clad layer 4 constitute a light emitting layer 12 having a double hetero structure. Where n-type Ga
A buffer layer (not shown) and a distributed Bragg reflection layer (DBR layer, not shown) may be provided between the As substrate 1 and the n-type AlGaInP cladding layer 2.

A p-type current spreading layer 5 is formed on the surface of the p-type cladding layer 4, and a transparent conductive layer 7 is formed on the current spreading layer 5. Through holes 11 (shown by broken lines in FIG. 2) are formed in the transparent conductive layer 7. A surface electrode 9 (shown by a solid line in FIG. 2) is formed in a region of the transparent conductive layer 7 including the through hole 11. Therefore, the surface electrode 9 is in contact with both the transparent conductive layer 7 and the current spreading layer 5 thereunder. When a compound semiconductor layer (not shown) is formed on the current spreading layer 5, the surface electrode 9 contacts the compound semiconductor layer. N-type Ga
A back electrode 10 is formed on the entire back surface of the As substrate 1.

In this embodiment, not only the metal layer 13 is formed inside the through hole 11, but also the metal layer 14 is formed around the through hole 11. Therefore, the surface electrode 9 is the metal layer 1
Current distribution layer 5 and transparent conductive layer 7 through 3 and 14, respectively
Touches. Both metal layers 13 and 14 are formed of a metal or an alloy thereof described later.

(2) Second Mode FIG. 3 is a vertical sectional view of a semiconductor light emitting device according to the second mode of the present invention. In the semiconductor light emitting device of this aspect, since the transparent conductive layer 7 is directly formed on the p-type cladding layer 4,
The surface electrode 9 is in contact with the p-type cladding layer 4 and the transparent conductive layer 7 via the metal layers 13 and 14, respectively. Since the other layers are the same as those in the first embodiment, the description thereof will be omitted.

(3) Third Mode FIG. 4 is a vertical sectional view of a semiconductor light emitting device according to the third mode of the present invention. In the semiconductor light emitting device of this aspect, the through hole 11
Only the metal layer 13 is formed inside, but no metal layer is formed around the through hole 11. Therefore, the surface electrode 9
Is in contact with the current spreading layer 5 via the metal layer 13 and is in direct contact with the transparent conductive layer 7. The other points are the same as those in the first embodiment, and thus the description thereof will be omitted.

(4) Fourth Mode FIG. 5 is a vertical sectional view of a semiconductor light emitting device according to a fourth mode of the present invention. In the semiconductor light emitting device of this aspect, the through hole 11
Only the metal layer 13 is formed inside, but no metal layer is formed around the through hole 11. Therefore, the surface electrode 9
Is in contact with the p-type cladding layer 4 via the metal layer 13 and is in direct contact with the transparent conductive layer 7. The other points are the same as those in the second embodiment, and thus the description thereof will be omitted.

(B) Each Layer (1) Substrate It is preferable that the material of the substrate is the same as that of the crystal layer constituting the epitaxial layer in characteristics such as thermal expansion coefficient and lattice constant.
Specifically, GaAs, GaP, InP and the like are preferable, and GaAs is particularly preferable.

(2) Light-Emitting Portion Layer The light-emitting portion layer 12 preferably has a pn-junction type double heterojunction structure. For example, when the substrate 1 is n-type GaAs, a clad layer of the first conductivity type (n-type) is used. Clad layer 2), active layer 3
And a second conductivity type clad layer (p-type clad layer 4). Further, the light emitting section layer 12 is preferably composed of a mixed crystal compound semiconductor. Specifically, AlGaIn
Mixed crystals of P, GaInP, GaInAsP, AlGaInAs, etc. are preferable, and AlG
More preferred are aInP and GaInP. In particular, (In _x Ga _1-x ) _0.5 In _0.5 P (0 ≤ x ≤ 1) with an indium composition ratio of about 0.5 is Ga
It is preferable because it is lattice-matched with the As single crystal substrate.

(3) Current Dispersion Layer The p-type current dispersion layer 5 is selected from materials having low absorption of emission wavelength and low specific resistance. Specifically, GaP, GaI
Compound semiconductors such as nP, AlInP, AlGaInP, GaAsP and AlGaAs are preferable. The current spreading layer 5 is preferably as thin as possible.

(4) Compound Semiconductor Layer The compound semiconductor layer comprises (1) a binary compound semiconductor of InP or InAs, (2) a ternary compound semiconductor of AlInAs or AlInP, (3)
At least one ternary compound semiconductor (molar ratio of Ga: 0.2 or less) selected from the group consisting of AlGaAs, AlGaP, GaInAs, and GaInP, (4) AlInAsP quaternary compound semiconductor, (5)
At least one quaternary compound semiconductor selected from the group consisting of AlGaInP, AlGaInAs, AlGaAsP, and GaInAsP (molar ratio of Ga: 0.2 or less), or (6) quaternary compound semiconductor composed of AlGaInAsP (molar ratio of Ga : 0.2 or less).

(5) Transparent Conductive Layer The specific resistance of the transparent conductive layer 7 is significantly lower than that of the current spreading layer 5. For example, the resistivity of the ITO layer is generally about 3 × 10 ^-6 Ωm
Which is about one hundredth of the specific resistance of the p-type GaP layer. Therefore, by using the transparent conductive layer 7, the thickness of the epitaxial semiconductor layer can be greatly reduced. The transparent conductive layer 7 is preferably made of an oxide such as tin oxide (SnO ₂ ), zinc oxide (ZnO), indium oxide (In ₂ O ₃ ), indium tin oxide (ITO), magnesium oxide (MgO),
Particularly, it is preferably made of indium tin oxide (ITO).

(6) Electrode (a) Surface electrode The surface electrode 9 is easy to connect (good bonding property), and low ohmic contact resistance with the lower layer can be stably obtained (good ohmic property). Also, good adhesion with the lower layer is required. In order to satisfy these, the surface electrode 9 is preferably a multi-layer electrode composed of a plurality of layers of metal (Au, Zn, Ni, Al, etc.), metal alloy (Au-Zn, etc.). In particular, the uppermost layer is preferably made of a metal having good bonding characteristics such as Au or Al. The multilayer electrode of the surface electrode may include a layer made of a metal oxide such as nickel oxide (NiO) or titanium oxide (TiO ₂ ).

(B) Back Surface Electrode Since the back surface electrode 10 is required to have good ohmic characteristics and adhesion like the front surface electrode, a plurality of layers of metal (Au, Ni, etc.), metal alloy (Au-Ge, etc.), etc. It is preferably a multilayer electrode composed of For example, an Au-Ge alloy, an electrode in which Ni and Au are sequentially laminated, and the like are preferable. The back surface electrode 10 is formed on the whole or a part of the back surface of the substrate, and the uppermost layer is preferably made of a metal having good bonding characteristics such as Au or Al.

(7) When the surface electrode 9 directly contacts the lower semiconductor layer (current distribution layer 5 etc.) through the through hole 11 of the metal layer transparent conductive layer 7, (1) a large amount of current flows from the semiconductor layer. The current dispersion effect tends to decrease, and (2) since the amount of light emitted from the light emitting portion directly below the surface electrode 9 increases, the efficiency of extracting the emitted light to the outside decreases. The metal layer 13 is provided in order to solve such a problem, and has the action of reducing the current flowing through the semiconductor layer by the metal layer 13 and suppressing the light emission immediately below the surface electrode 9.

Therefore, the metal layer 13 is made of Ti, Zr, Mo, Ta,
It is preferably composed of at least one selected from the group consisting of W, Pt, Ir, Os, Re, Rh, Pd and alloys thereof,
In particular, it is preferably made of Ti or its alloy. The reason why the metal layer 13 intervenes to suppress the light emission immediately below the surface electrode 9 is not clear, but it is presumed that the interposition of the metal layer 13 increases the forward voltage VF.

The transparent conductive layer 7 may be composed of a plurality of ITO films, in which case the uppermost ITO film has a high specific resistance. Therefore, the metal layer 13 needs to be thick enough not to contact the uppermost ITO film. The same thing can be said with respect to the thickness that does not make contact, even when the transparent conductive layer 7 is composed of a single-layer ITO film. In this case,
The metal layer is preferably not in contact with the uppermost part of the transparent conductive layer. Specifically, the metal layer 13 preferably has a thickness of 0.01 to 0.1 μm.

[2] Method for Manufacturing Semiconductor Light-Emitting Element (1) Formation of Epitaxial Layer Preferred methods for forming an epitaxial layer include solid phase epitaxial growth method, liquid phase epitaxial growth method and vapor phase epitaxial growth method. From the viewpoint of quality and uniformity, the vapor phase epitaxial growth method is more preferable. Specifically, a metal organic vapor phase epitaxial growth method (MOVPE method), a molecular beam epitaxial growth method (MBE method) and the like are preferable.

(2) Formation of Transparent Conductive Layer Having Through Hole The transparent conductive layer 7 having the through hole 11 is formed on the light emitting part layer (when a current dispersion layer and / or a compound semiconductor layer is provided thereon). ) Can be prepared by a known method. For example, the transparent conductive layer 7 is formed by a coating method (spin method, dip method, roller method, spray method, etc.), a resist mask is further exposed, and then the through hole 11 is formed by etching. A method for directly forming the transparent conductive layer 7 having a desired through hole 11 by the vapor deposition method used, a method for forming the transparent conductive layer 7 by a coating method (spin type, dip type, roller type, spray type, etc.) Examples include a method of removing a part of the transparent conductive layer 7 by a film removal method such as milling to form the through holes 11, a method of combining any of these known methods, and the like.

The shape of the through hole 11 is not particularly limited, and may be circular,
It is possible to provide any shape such as a square (square, rhombus, polygon, etc.), a shape in which a protrusion is attached to a circle or a square, a ring shape, or the like. Further, the number of through holes 11 need not be one.

(3) Formation of Metal Layer and Electrode First, Ti, Zr, Mo, Ta, W, Pt, Ir, Os, Re, is formed in a region including the inside of the through hole 11 of the transparent conductive layer 7 or its peripheral portion. Rh, P
The surface electrode 9 is formed by depositing a metal layer 13 of at least one selected from the group consisting of d and these alloys, and then depositing a conductive metal or its alloy.
The back surface electrode 10 is formed by depositing a similar conductive metal or its alloy on the back surface of the substrate 1. As a vapor deposition method,
A high frequency sputtering method, an ion plating method, an electron beam (EB) vapor deposition method, a vacuum vapor deposition method and the like can be mentioned.

The surface electrode 9 is a layer under the transparent conductive layer 7 via the metal layer 13, for example, the light emitting layer 4 (in the case of FIGS. 3 and 5), the current spreading layer 7 (in the case of FIGS. 1 and 4) or the compound. When the metal layer 14 is formed in contact with a semiconductor layer (not shown) and also in the peripheral portion of the through hole 11 of the transparent conductive layer 7, the metal layer 14 is in contact with the transparent conductive layer 7.

In order to obtain a sufficient bonding strength between the surface electrode 9 and the lower layer via the metal layer 13, the area of the through hole 11 (the total area when a plurality of through holes 11 are provided) is equal to that of the surface electrode 9. It is preferably 1% or more of the area, and more preferably 20 to 95%. If the area of the through hole 11 is less than 1%, the surface electrode
No improvement in peel resistance can be obtained. On the other hand, when the area of the through holes 11 exceeds 95%, the transparent conductive layer 7 made of metal oxide is formed.
The current distribution effect of is insufficient and the color output is lowered.

From the viewpoint of uniform current dispersion, the surface electrode 9
It is preferable that the center of the through hole 11 and the center of the through hole 11 (the center of the region surrounded by all the through holes 11 when a plurality of through holes 11 are provided) substantially coincide with each other.

In order to impart ohmic properties to the electrodes, heat treatment (alloying) may be performed in an inert atmosphere such as nitrogen gas or argon gas.

[0044]

The present invention will be described in more detail by the following examples, but the present invention is not limited thereto.

Example 1 A red light emitting diode having a structure shown in FIG. 1 (emission wavelength 630 nm
Was prepared by MOVPE method.

(1) Fabrication of epitaxial wafer First, on the first main surface of the n-type GaAs substrate 1 heated to 700 ° C., the thickness
500 nm n-type (Se-doped) GaAs buffer layer, thickness 500
nm n-type (Se-doped) (Al_0.7Ga_0.3)_0.5In_0.5P-clad
Layer 2 (Se doping amount: 1.0 × 10¹⁸cm^-3), The thickness of 600 nm
Dope (Al_0.15Ga_0.85)_0.5In_0.5P active layer 3, thickness 500 n
m p-type (zinc-doped) (Al_0.7Ga_0.3)_0.5In _0.5P-clad
Layer 4 (Zinc doping amount: 5 × 10¹⁷cm^-3), And 2 μm thick
p-type (zinc-doped) GaP current spreading layer 5 (zinc-doped amount: 5
× 10¹⁸cm^-3) Are sequentially grown by MOVPE method.
Lengthened Light emitting layer 12 (clad layer 2, light emitting layer 3,
MOVPE growth of the dead layer 4) is carried out at a temperature of 700 ° C and 50 Torr.
The growth rate was 0.3 to 1.0 nm / sec at pressure. Supply
The ratio of the group V element to the group III element (V / III ratio) is 300-600.
It was in the range. Also, the GaP current dispersion layer 5 has a growth rate of 1 nm.
/ Sec, V / III ratio 100.

Hydrogen is used as a carrier gas, and
Trimethyl aluminum (TMA) as a source, trimethyl gallium (TMG) as a Ga source, trimethyl indium (TMI) as an In source, arsine (AsH ₃ ) as an As source, phosphine (PH ₃ ) as a P source, Zn Diethyl zinc (DEZ) as a source and H ₂ S as a source of Se
used e.

(2) Preparation of transparent conductive layer An ITO film was formed on the surface of the epitaxial wafer prepared as described above by repeatedly applying the ITO solution three times using a spin coater. Epitaxial wafer with ITO film formed is 2 × 10 ^-6 Torr (2.7 × 10 ^-4 Pa)
Was baked at 500 ° C. for 1 hour in vacuum to form an ITO transparent conductive layer 7 having a thickness of 0.3 μm.

(3) Preparation of surface electrode Through hole 1 is formed in ITO transparent conductive layer 7 by photolithography.
1 was produced. In the photolithography method, a resist mask having two-dimensional circular openings with a diameter of 125 μm is formed on the ITO transparent conductive layer 7 at regular intervals, and after exposure, an etching solution of hydrochloric acid / nitric acid / pure water is used to form the resist mask. The ITO film exposed in the circular opening was removed to form the through hole 11. After removing the resist mask, a resist mask having a circular opening with a diameter of 135 μm whose center coincides with the through hole 11 was formed on the ITO film.

First, in the circular opening of the resist mask,
After forming the metal layer 13 by depositing 20 nm of Ti, nickel having a thickness of 10 nm and gold having a thickness of 1000 nm were sequentially deposited to form a circular surface electrode 9 having a diameter of 135 μm. Finally, the resist mask was removed. The area of the through hole 11 (the contact area between the metal layer 13 and the current spreading layer 5) was about 86% of the area of the surface electrode 9.

(4) Formation of Backside Electrode A gold-germanium alloy with a thickness of 60 nm, nickel with a thickness of 10 nm and gold with a thickness of 500 nm are sequentially deposited on the entire backside of the substrate 1 to form an n-type backside electrode. Formed 10.

Furthermore, in order to impart ohmic properties to the front surface electrode 9 and the rear surface electrode 10, the temperature is 5 ° C. at 400 ° C. in a nitrogen gas atmosphere.
A heat treatment (alloying) for 1 minute was performed.

(5) Fabrication and Evaluation of Semiconductor Light Emitting Element The epitaxial wafer having both electrodes 9 and 10 formed as described above was diced into a 300 μm square size including one surface electrode 9 and fixed to a frame, The front surface electrode 9 was wire-bonded, and the back surface electrode 10 was die-bonded to manufacture a light emitting diode chip. Forward operating voltage of the obtained LED chip (at 20 mA current)
Was 1.87 V and the emission output was 2.6 mW.

Example 2 As the current spreading layer 5, p-type (zinc-doped) GaP having a thickness of 2 μm was used.
Instead of a film, a 2 μm thick p-type (zinc-doped) (Al _0.7 Ga
A light emitting diode having a structure shown in FIG. 1 was produced in the same manner as in Example 1 except that a _0.3 ) _0.5 In _0.5 P (zinc doping amount: 1.0 × 10 ¹⁸ cm ⁻³ ) film was formed. The forward operating voltage (at 20 mA current application) of the obtained light emitting diode chip was 1.90 V, and the light emission output was 2.6 mW.

Example 3 A red light emitting diode having an emission wavelength of about 630 nm having the structure shown in FIG. 1 was produced by the following procedure. First, on a first main surface of a p-type GaAs substrate 1 heated to 700 ° C., a p-type (Zn
Doped) GaAs buffer layer, thickness 500 nm of the p-type _{(Zn-doped) (Al 0.7 Ga 0.3) 0.} 5 In 0.5 P cladding layer 2 (Zn doping ^{amount: 1.0 × 10 18 cm -3)} , a thickness of 600 nm Undoped (Al _0.15
Ga _0.85 ) _0.5 In _0.5 P active layer 3, 500 nm thick n-type (Se-doped) (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 4 (Se doping amount: 5 × 10 ¹⁷ cm ^-3 ), and 2μm thick n-type (Se-doped)
(Al _0.7 Ga _0.3 ) _0.5 In _0.5 P Current distribution layer 5 (Se doping amount: 1.0
X 10 ¹⁸ cm ^-3 ) was sequentially epitaxially grown by the MOVPE method under the same conditions as in Example 1. The layer structure up to here is
Other than the polarity of each layer, it is the same as that of the first embodiment.

Then, in the same manner as in Example 1, the thickness is 0.3 μm.
The ITO transparent conductive layer 7 was formed, and the through holes 11 having a diameter of 125 μm were formed therein. 135 μm diameter with center aligned with through hole 11
A resist mask having a circular opening is formed on the ITO transparent conductive layer 7, and Ti is vapor-deposited in and around the through hole 11 to form a metal layer 13 having a thickness of 20 nm.
A circular surface electrode 9 having a diameter of 135 μm was formed by sequentially depositing nickel having a thickness of nm and gold having a thickness of 1000 nm. Finally, the resist mask was removed. Area of through hole 11 (metal layer
The contact area between 13 and the current distribution layer 5) was about 86% of the area of the surface electrode 9.

A 60-nm-thick gold-zinc alloy, a 10-nm-thick nickel, and a 500-nm-thick gold were sequentially deposited on the entire back surface of the substrate 1 to form an n-type back electrode 10. Furthermore, in order to impart ohmic properties to the front surface electrode 9 and the back surface electrode 10,
Heat treatment (alloying) was performed at 400 ° C. for 5 minutes in a nitrogen gas atmosphere.

A light emitting diode chip was produced from the epitaxial wafer having both electrodes 9 and 10 formed by the same method as in Example 1. The obtained light emitting diode had a forward operating voltage of 1.86 V at a current of 20 mA and an emission output of 2.6 mW.
Met.

Example 4 A red light emitting diode having an emission wavelength of about 630 nm having the structure shown in FIG. 4 was produced by the following procedure. First, on a first main surface of a p-type GaAs substrate 1 heated to 700 ° C., a p-type (Zn
Doped) GaAs buffer layer, thickness 500 nm of the p-type _{(Zn-doped) (Al 0.7 Ga 0.3) 0.} 5 In 0.5 P cladding layer 2 (Zn doping ^{amount: 1.0 × 10 18 cm -3)} , a thickness of 600 nm Undoped (Al _0.15
Ga _0.85 ) _0.5 In _0.5 P active layer 3, 500 nm thick n-type (Se-doped) (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 4 (Se doping amount: 5 × 10 ¹⁷ cm ^-3 ), and 2μm thick n-type (Se-doped)
(Al _0.7 Ga _0.3 ) _0.5 In _0.5 P Current distribution layer 5 (Se doping amount: 1.0
X 10 ¹⁸ cm ^-3 ) was sequentially epitaxially grown by the MOVPE method under the same conditions as in Example 1. The layer structure up to here is
Other than the polarity of each layer, it is the same as that of the third embodiment.

Then, in the same manner as in Example 1, the thickness is 0.3 μm.
The ITO transparent conductive layer 7 was formed, and the through holes 11 having a diameter of 125 μm were formed therein. A resist mask having a circular opening with a diameter of 125 μm, which corresponds to the through hole 11, is formed on the ITO transparent conductive layer 7, and Ti is vapor-deposited to a thickness of 20 n
A metal layer 13 of m was formed. After removing the resist mask, a resist mask having a circular opening with a diameter of 135 μm whose center coincides with the through hole 11 is formed on the ITO transparent conductive layer 7 again, and a thickness of 10 nm is formed in and around the through hole 11. Of nickel and gold with a thickness of 1000 nm are deposited in sequence to obtain a diameter of 1
A 35 μm circular surface electrode 9 was formed. Finally, the resist mask was removed. The area of the through hole 11 (the contact area between the metal layer 13 and the current spreading layer 5) was about 86% of the area of the surface electrode 9.

A 60 nm-thick gold-zinc alloy, a 10 nm-thick nickel and a 500 nm-thick gold were sequentially deposited on the entire rear surface of the substrate 1 to form an n-type rear surface electrode 10. Furthermore, in order to impart ohmic properties to the front surface electrode 9 and the back surface electrode 10,
Heat treatment (alloying) was performed at 400 ° C. for 5 minutes in a nitrogen gas atmosphere.

A light emitting diode chip was manufactured from the epitaxial wafer having both electrodes 9 and 10 formed by the same method as in Example 1. 20 m of the obtained light emitting diode chip
The forward operating voltage when A is energized is 1.84V, and the light emission output is 2.
It was 8 mW.

Comparative Example 1 A red light emitting diode having an emission wavelength of about 630 nm having the structure shown in FIG. 6 was produced in the same manner as in Example 1 except that the metal layer 13 was not formed. The obtained light emitting diode had a forward operating voltage of 1.85 V when energized at 20 mA, but had a low emission output of 2.1 mW.

Comparative Example 2 As the current spreading layer 5, p-type (zinc-doped) GaP having a thickness of 2 μm was used.
Instead of the film, 2.0 μm thick p-type (zinc-doped) (Al _0.7 G
a _{0.3) 0.5} In _0.5 P (zinc-doped ^{amount: 1.0 × 10 18 cm - 3} ) in the same manner as in Comparative Example 1 except that film was formed, to prepare a light-emitting diode. The obtained light emitting diode had a forward operating voltage of 1.89 V when energized at 20 mA, but had a low emission output of 2.1 mW.

Although the semiconductor light emitting device of the present invention has been described with reference to the accompanying drawings, the present invention is not limited to them, and various modifications can be made within the scope of the technical idea of the present invention. . For example, the same effect can be obtained by providing a vapor deposition layer made of Zr, Mo, Ta, W, Pt, Ir, Os, Re, Rh, Pd, or an alloy thereof in addition to providing a vapor deposition layer of Ti as the metal layer. can get. Further, the shape and number of the through holes are not limited to the illustrated example.

[0066]

As described above, in the semiconductor light emitting device of the present invention in which the metal layer and the surface electrode are sequentially formed after forming the through hole in the transparent conductive layer, (1) the surface electrode is formed as a lower layer through the through hole. Since it is in direct contact, there is no problem of peeling of the surface electrode due to dicing, wire bonding, etc., and (2) the surface electrode is in contact with the lower layer via a metal layer such as Ti, so that the current dispersion is improved, Low forward operating voltage and brightness of about 30%
It has the advantage of being higher.

The epitaxial layer of the semiconductor light emitting device of the present invention having a transparent conductive layer having a low specific resistance such as ITO is about one fifth to several tenths of the thickness of the conventional epitaxial layer for semiconductor light emitting device. Since it can be thinned, it contributes to cost reduction of the epitaxial wafer.

[Brief description of drawings]

1 is a cross-sectional view showing a semiconductor light emitting device according to an embodiment of the present invention, which corresponds to the AA cross-sectional view of FIG.

FIG. 2 is a plan view showing a semiconductor light emitting device according to an embodiment of the present invention.

FIG. 3 is a sectional view showing a semiconductor light emitting device according to another embodiment of the present invention.

FIG. 4 is a sectional view showing a semiconductor light emitting device according to still another embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a semiconductor light emitting device according to still another embodiment of the present invention.

FIG. 6 is a sectional view showing a semiconductor light emitting device before the present invention is applied.

FIG. 7 is a cross-sectional view showing a conventional semiconductor light emitting device.

[Explanation of symbols]

1 ... Substrate 2, 4 ... Clad layer 3 ... Active layer 5 ... Current distribution layer 7: Transparent conductive layer 9 ... Surface electrode 10 ... Back electrode 11 ... Through hole 12 ... Light emitting layer 13 ... Metal layer

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kenji Shibata             Hitachi, 1-1 Hidaka-cho, Hitachi City, Ibaraki Prefecture             Electric Wire Co., Ltd. Hidaka Factory F-term (reference) 5F041 AA43 CA34 CA65 CA85 CA88                       CA92 CA98

Claims (13)

[Claims] 1. A first-conductivity-type substrate on which a back electrode is formed, a light-emitting portion layer formed of an active layer sandwiched between a pair of cladding layers, a transparent conductive layer formed of a metal oxide film, and a front electrode. In the formed semiconductor light emitting device, the transparent conductive layer has at least one through hole, and Ti, Z are provided in the through hole.
A layer made of at least one metal selected from the group consisting of r, Mo, Ta, W, Pt, Ir, Os, Re, Rh, Pd and alloys thereof is formed, and the surface electrode is made of the metal. A semiconductor light emitting device, which is in contact with the light emitting portion layer through a layer. 2. The semiconductor light emitting device according to claim 1, wherein Ti, Zr, Mo, Ta, W, Pt, Ir are also formed in a region on the transparent conductive layer around the through hole and in contact with the surface electrode. ， O
A semiconductor light emitting device, wherein a layer made of at least one metal selected from the group consisting of s, Re, Rh, Pd and alloys thereof is formed. 3. The semiconductor light emitting device according to claim 1 or 2, wherein the metal layer is made of Ti or an alloy thereof. 4. The semiconductor light emitting device according to claim 1, wherein a current diffusion layer of a second conductivity type is formed between the light emitting section layer and the transparent conductive layer, and the surface is provided. The semiconductor light emitting device, wherein the electrode is in contact with the current spreading layer through the metal layer formed in the through hole. 5. The semiconductor light emitting device according to claim 1, wherein a compound semiconductor layer is formed between the light emitting section layer and the transparent conductive layer, and the surface electrode has the through hole. A semiconductor light emitting device, which is in contact with the compound semiconductor layer through a metal layer formed therein. 6. The semiconductor light emitting device according to claim 4, wherein a compound semiconductor layer is formed between the current spreading layer and the transparent conductive layer, and the surface electrode is formed in the through hole. A semiconductor light emitting device, which is in contact with the compound semiconductor layer through a metal layer. 7. The semiconductor light emitting device according to claim 1, wherein the light emitting section layer is sandwiched between a first conductivity type clad layer, a second conductivity type clad layer, and both clad layers. And a semiconductor active layer. 8. The semiconductor light emitting device according to claim 1, wherein an area of the through hole (a total area when there are a plurality of through holes) is 1% or more of an area of the surface electrode. A semiconductor light emitting device characterized by being present. 9. The semiconductor light emitting device according to claim 1, wherein a center of a region of the light emitting section layer, the current spreading layer, or the compound semiconductor layer in contact with the surface electrode, and the surface electrode. A semiconductor light-emitting device characterized by being substantially coincident with the center of. 10. The semiconductor light emitting element according to claim 1, wherein the substrate is made of GaAs, and the light emitting section layer is made of AlGaInP or GaInP. 11. The semiconductor light emitting device according to claim 1, wherein the current spreading layer is GaP, GaAlP, AlIn.
A semiconductor light emitting device comprising at least one compound semiconductor selected from the group consisting of P, AlGaInP, AlGaAs and GaAsP. 12. The semiconductor light emitting device according to claim 1, wherein the compound semiconductor layer is (1) InP or InAs binary compound semiconductor, (2) AlInAs or AlInP ternary compound semiconductor, (3) At least one ternary compound semiconductor (molar ratio of Ga: 0.2 or less) selected from the group consisting of AlGaAs, AlGaP, GaInAs, and GaInP, (4) AlInAsP quaternary compound semiconductor, (5) AlGaInP, AlGaInAs, AlGaAsP and GaInAsP
At least one quaternary compound semiconductor selected from the group consisting of (molar ratio of Ga: 0.2 or less) or (6) quaternary compound semiconductor composed of AlGaInAsP (molar ratio of Ga: 0.2 or less). A semiconductor light emitting device characterized in that 13. The semiconductor light emitting device according to claim 1, wherein the metal oxide forming the transparent conductive layer is selected from the group consisting of SnO ₂ , In ₂ O ₃ , ITO and Ga-containing ZnO. At least one selected from the group consisting of semiconductor light emitting devices.