JP2000058918A - Semiconductor light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure for a lower-part electrode which can be used as the lower-part electrode of a light emitting element by forming a metal electrode on an insulating substrate. SOLUTION: A comb teeth-shaped or lattice-shaped electrode film 23 is formed on an insulating substrate 22. A GaN layer (a light emitting layer) 24 is formed on the insulating substrate 22 via the electrode film 22, Then while the exposed region of the insulating substrate 22 is used as a substrate crystal, the GaN layer 24 is epitaxially grown. An upper-part electrode 26 is formed on the surface of the GaN layer 24. A DC voltage is applied across the electrode film 23 and the upper-part electrode 26 so as to emit light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] The present invention relates to a semiconductor light emitting device. In particular,
III-V compounds of GaN, InGaN, GaAlN,
The present invention relates to a semiconductor light emitting device using InGaAlN or the like.

[0002]

2. Description of the Related Art As a material of a semiconductor light emitting device such as a light emitting diode (LED) or a laser diode (LD) that generates blue light or ultraviolet light, a general formula InxGayAlz is used.
N (however, x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦
III-V group compound semiconductors represented by 1, 0 ≦ z ≦ 1) are known. Since this compound semiconductor is a direct transition type, it has high luminous efficiency, and its emission wavelength can be controlled by the In concentration.

[0003] Since it is difficult to produce a large single crystal of InxGayAlzN, a so-called heteroepitaxial growth method for growing a crystal film on a substrate of a different material is used. It is grown on a planar sapphire substrate.

However, since the sapphire substrate is an insulator, it is impossible to provide an upper electrode and a lower electrode on the upper surface of the light emitting element and the lower surface of the substrate, respectively, as in a light emitting diode having a general structure.

For this reason, a conventional semiconductor light emitting device (laser diode) formed on a sapphire substrate has a structure as shown in FIG. In this semiconductor light emitting device 1, a ZnO buffer layer 3 doped with Al at a high concentration is formed on a sapphire substrate 2, and an n-type GaN layer (contact layer) 4 and an n-type AlGaN layer (clad Layer) 5, n-type GaN layer (light guide layer) 6, I
nGaN (light-emitting layer) 7, p-type GaN layer (light guide layer)
8, a p-type AlGaN layer (cladding layer) 9, a p-type GaN layer (contact layer) 10, and a SiO ₂ layer 11 are sequentially grown. This n-type GaN layer 4, n-type AlGaN layer 5, n
Light-emitting element 1 by the p-type GaN layer 6, the InGaN layer 7, the p-type GaN layer 8, the p-type AlGaN layer 9, and the p-type GaN layer 10.
A double heterojunction structure, which is the main part of the structure, is constructed. Further, since the sapphire substrate 2 is an insulator and a lower electrode cannot be provided on the lower surface of the sapphire substrate 2, the n-type GaN layer 4 to the SiO ₂ layer 11 are etched to partially expose the ZnO buffer layer 3. , Zn
The lower electrode 12 is provided on the exposed portion of the O layer 3. on the other hand,
The SiO ₂ layer 11 is partially opened, and p
SiO ₂ layer 11 so as to be bonded to
The upper electrode 14 is provided on the substrate. The upper electrode 14
It has a current confinement structure including a ZnO layer 15 and an Au layer 16 which are heavily doped with 1 and injecting a current from the upper electrode 14 to the p-type GaN layer 10 through the opening 13 of the SiO ₂ film 11 as an insulator.

[0006]

In the semiconductor light emitting device 1 having such a structure, the ZnO buffer layer 3 is provided with an n-type GaN layer 4 having good crystallinity above the sapphire substrate 2 by relaxing lattice mismatch. Has the function of a contact layer for providing the lower electrode 12 at the same time as the function of a buffer layer for growing
Is heavily doped.

[0007] Therefore, Al doped in the ZnO buffer layer 3 diffuses into the n-type GaN layer 4 and the n-type AlGaN layer 5 to change the composition of these compound semiconductor layers, thereby changing the physical properties and optical properties of the light emitting device. There was a problem of changing the characteristics. Furthermore, the ZnO buffer layer 3 with reduced resistance
Then, it was also difficult to lower the resistance of a generally used metal electrode.

The present invention has been made to solve the above-mentioned technical problems, and an object of the present invention is to provide a semiconductor light emitting device formed on an insulating substrate, wherein a metal electrode can be used on the substrate side. It is to make.

[0009]

DISCLOSURE OF THE INVENTION In the semiconductor light emitting device of the present invention, a metal film is partially formed on an insulating substrate, and InxGayAlzN (where x + y + z =
1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1). Forming a metal film partially means typically forming the metal film in a comb-like shape or in a lattice shape.

In this light emitting device, since a metal film is formed on an insulating substrate, this metal film can be used as an electrode on the substrate side. In addition, since the metal film is only partially formed on the insulating substrate, the surface of the insulating substrate is exposed from the metal film. Therefore, when a compound semiconductor layer is formed over an insulating substrate via a metal film, the compound semiconductor layer grows in crystal from an exposed region of the insulating substrate, and a compound semiconductor layer with good crystallinity can be obtained.

In addition, since the metal film can be used as an electrode, an impurity for lowering the resistance has an adverse effect on the compound semiconductor layer, as in the case of using a lower resistance semiconductor layer, or the resistance cannot be sufficiently lowered. The problem is solved.

According to the semiconductor light emitting device of the present invention, a ZnO buffer layer is provided on an insulating substrate.
A metal film is partially formed on the O buffer layer, and InxGayAlzN is formed on the ZnO buffer layer through the metal film.
(However, x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1,
A compound semiconductor layer represented by 0 ≦ z ≦ 1) is formed.

In this semiconductor light emitting device, since the ZnO buffer layer is provided on the insulating substrate, the lattice mismatch between the insulating substrate and the compound semiconductor layer is reduced in addition to the effect of the semiconductor light emitting device of the first aspect. As a result, a compound semiconductor layer having good crystallinity can be grown. Further, a compound semiconductor layer can be formed over various insulating substrates.

[0014]

FIG. 2 is a sectional view showing a semiconductor light emitting device 21 according to one embodiment of the present invention, which is a light emitting diode (LED) or a surface emitting laser diode (LD).
And the like. In the semiconductor light emitting device 21, a C-plane sapphire substrate, an R-plane sapphire substrate, or the like is used as the insulating substrate 22. On the insulating substrate 22, an electrode film 23 is partially formed of a metal having a small specific resistance, such as Al or Au. The electrode film 23 is obtained by forming a vapor deposition film of, for example, Al or Au on the insulating substrate 22 and then patterning the film by a photolithography process. As the electrode film 23, for example, as shown in FIGS. 3A and 3B, a comb-like (blind) or lattice-like film can be used.

The ratio A / (A + B) of the width A of the electrode finger to the width B of the gap is preferably between 0.3 and 0.7. If the gap ratio A / (A + B) is too large, the exposed region of the insulating substrate becomes too narrow, and the crystallinity of the crystal growth of the semiconductor light emitting layer formed thereon deteriorates. Conversely, if the gap ratio A / (A + B) is too small, the electrode area will be small, and the electrode will have a high resistance. As a result of examining a preferable range of numerical values from these viewpoints, it was found that 0.3 to
The inventors have found that a range of 0.7 is preferable as a result of investigations. For example, the width A of the electrode and the width B of the gap may both be 6 μm, or the width A of the electrode may be 8 μm and the width B of the gap may be 4 μm.

Thereafter, the insulating substrate 22 is interposed via the electrode film 23.
A GaN layer (light-emitting layer) 24 is epitaxially grown thereon. The electrode substrate 23 is formed in a comb-like or lattice-like shape to form the insulating substrate 2.
2, the GaN layer 24 grows using the exposed region 25 of the insulating substrate 22 as a base crystal, so that the GaN layer 24 having good crystallinity grows epitaxially.

Thereafter, an upper electrode 26 made of a metal film is formed on the upper surface of the GaN layer 24. When a DC voltage is applied between the upper electrode 26 provided on the upper and lower surfaces of the GaN layer 24 and the lower electrode (electrode film 23) using the electrode film 23 as a lower electrode, a current is injected into the GaN layer 24 to emit light. And
Light emitted from the GaN layer 24 is emitted outside from a region on the upper surface of the GaN layer 24 where the upper electrode 26 is not provided.

(Second Embodiment) FIG. 5 is a sectional view showing a semiconductor light emitting device 27 according to another embodiment of the present invention.
Also in this semiconductor light emitting element 27, a C-plane sapphire substrate, a Si substrate, a glass substrate, an alumina substrate, or the like is used as the insulating substrate 22. C on this insulating substrate 22
An axially oriented ZnO buffer layer 28 is provided, and an electrode film 23 is formed partially on the ZnO buffer layer 28 with a metal having a small specific resistance, such as Al or Au.
Or in a grid pattern. Then, the electrode film 23
A GaN layer 24 (light-emitting layer) is epitaxially grown on the ZnO buffer layer 28 through the substrate, and an upper electrode 26 is formed on the upper surface of the GaN layer 24.

In this embodiment, since the ZnO buffer layer 28 is provided between the insulating substrate 22 and the electrode film 23,
The GaN layer 24 grows from the exposed region 29 of the nO buffer layer 28. The lattice constant of the ZnO single crystal in the a-axis direction is closer to the lattice constant of GaN in the a-axis direction than the insulating substrate 22 such as a sapphire substrate (generally, InxGayA
The same applies to lzN. ), The ZnO on the insulating substrate 22
By providing the buffer layer 28, the GaN layer 24 having better crystallinity can be grown, and the semiconductor element 27 having good characteristics can be obtained. Also, the insulating substrate 22
By providing the ZnO buffer layer 28 on the substrate, various insulating substrates 22 can be used.

(Third Embodiment) FIG. 6 shows a third embodiment of the present invention.
FIG. 9 is a perspective view showing a semiconductor light emitting device 30 according to another embodiment.
There are edge emitting type light emitting diodes and laser diodes.
1 shows an edge-emitting semiconductor light emitting device 30 such as a semiconductor light emitting device.
You. In the light emitting element 30, on the insulating substrate 22,
An electrode film 23 having a comb shape or a lattice shape is formed, and an n-type GaN crystal is formed.
Rad layer 31, p-type GaN active layer 32, p-type GaN
And the mirror surface is formed by dicing.
Excluding the center of the upper surface of the p-type GaN cladding layer 33
SiO in the area _TwoA film 34 is formed. And n-type G
aN cladding layers 31-SiO_TwoThe film 34 is partially removed, and
The electrode film 23 is partially exposed to form a lower electrode,_TwoMembrane 3
4 on the p-type GaN cladding layer 33.
5 are provided. Then, the upper electrode 35 and the electrode film 23 are
Light is emitted by applying a voltage between them.

(Others) In the above embodiment, the light emission mechanism is constituted by a single GaN layer.
A light emitting mechanism having a heterojunction structure including an aN layer and a p-type GaN layer may be used (not shown). Or n
A light emitting mechanism having a double heterojunction structure including a p-type GaN layer, an n-type AlGaN layer, an InGaN layer (light-emitting layer), a p-type AlGaN layer, and a p-type GaN layer may be used (not shown).

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a structure of a conventional semiconductor light emitting device.

FIG. 2 is a cross-sectional view illustrating a structure of a semiconductor light emitting device according to an embodiment of the present invention.

FIG. 3 is a plan view showing a shape of an electrode film in the embodiment.

FIG. 4 is a plan view showing another shape of the electrode film.

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

FIG. 6 is a perspective view illustrating a structure of a semiconductor light emitting device according to another embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 22 insulating substrate 23 electrode film 24 GaN layer 26 upper electrode 28 ZnO buffer layer

Claims (4)

[Claims] A metal film is partially formed on an insulating substrate, and InxGayAl is formed on the insulating substrate via the metal film.
zN (where x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦
1. A semiconductor light emitting device comprising a compound semiconductor layer represented by the following formula: 1, 0 ≦ z ≦ 1). 2. A ZnO buffer layer is provided on an insulating substrate, a metal film is partially formed on the ZnO buffer layer, and Inx is formed on the ZnO buffer layer via the metal film.
GayAlzN (where x + y + z = 1, 0 ≦ x ≦ 1,
A semiconductor light emitting device comprising a compound semiconductor layer represented by 0 ≦ y ≦ 1, 0 ≦ z ≦ 1). 3. The semiconductor light emitting device according to claim 1, wherein the metal film is formed in a comb shape. 4. The semiconductor light emitting device according to claim 1, wherein said metal film is formed in a lattice shape.