JP2000174333A - Gallium nitride compound semiconductor light-emitting element and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate chip-formation by a method, wherein an active layer is formed on an n-GaN clad layer, and a p-GaN clad layer, a connection layer, and a conductive substrate are sequentially formed thereon, and a first electrode is formed on the conductive substrate, and at the same time a second electrode is formed on a part of the n-GaN clad layer. SOLUTION: A GaN buffer layer 13 is formed on a sapphire substrate 14, and a double heterostructure is formed which comprises an n-GaN clad layer 11, an InGaN active layer 10, and a P-GaN clad layer 9 on the GaN buffer layer 13. An Au connection layer 8 is formed through a vapor-deposition method on the P-GaN clad layer 9, and is closely adhered to the Au connection layer 8 in a pressurized state, annealed, so that GaAs conductive substrates 7 are stuck to each other. Thereafter, a sapphire substrate 14 and a GaN buffer layer 13 are removed to form an n electrode 1 in a part of the n-GaN clad layer 11 exposed, and also a p-electrode 4 is formed on the GaAs conductive substrate 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a gallium nitride-based AlxG.
The present invention relates to an ayIn1-x-yN (0 ≦ x, y ≦ 1, x + y ≦ 1) compound semiconductor light emitting device structure and a method of manufacturing the same.

[0002]

2. Description of the Related Art Light emitting diodes ranging from green to blue regions
As a material for (LED), AlxGayIn1-x-yN (0 ≦ x, y ≦ 1, x + y ≦ 1), which is a gallium nitride-based compound semiconductor, is used. This material is said to have a direct transition type band structure, and has high emission intensity. This material, which is expected to be developed as a material for a high-brightness light-emitting element, has also attracted attention in terms of its use as an electronic device in a current, voltage, and frequency range exceeding the theoretical limits of silicon. AlxGay
The crystal growth temperature of the In1-x-yN (0 ≦ x, y ≦ 1, x + y ≦ 1) compound semiconductor material is from 700 ° C. to 800 ° C., particularly GaN has a high value of 1200 ° C. Therefore, sapphire or SiC is used as a stable substrate material that does not deteriorate even at high temperatures. FIG.
2 is a sectional view showing the structure of a conventional gallium nitride-based compound semiconductor light emitting device. Because of the insulating property of the sapphire substrate 14, both the p-electrode 4 and the n-electrode 1 are formed on the crystal growth surface side opposite to the sapphire substrate side. Double heterostructure is n-Ga
A transparent electrode 27 and a current blocking insulating film 28 are formed on the p-GaN cladding layer 9 in order to allow current to flow therethrough, comprising an N cladding layer 11, an active layer 10, and a p-GaN cladding layer 9. The p-electrode 4 is formed on a part of the transparent electrode 27 and on the insulating film 28. A method for manufacturing this conventional light emitting device will be described. First, the GaN buffer layer 13 and n
-GaN cladding layer 11, AlxGayIn1-x-yN (0 ≦ x, y ≦ 1, x + y ≦
1) The active layer 10 and the p-GaN cladding layer 9 are sequentially crystal-grown. AlxGayIn1-x-yN (0 ≦ x, y ≦ 1, x + y ≦ 1) active layer 1
0 and a part of the p-GaN cladding layer 9 are removed by etching to obtain nG
A part of the aN cladding layer 11 is exposed. Exposed n-GaN
An n-electrode 1 is formed on a part of the cladding layer 11. p-Ga
On the N cladding layer 9, a transparent electrode 27 and a current blocking insulating film 28 are formed. The P electrode 4 is formed on a part of the transparent electrode 27 and on the insulating film 28 for blocking current.

FIG. 11 is a sectional view showing a schematic structure of an LED using a conventional gallium nitride-based compound semiconductor light emitting device. The semiconductor light-emitting element has a lead 24 with the p-electrode 4 side facing up.
And the p electrode 4 is connected to the bonding wire 25
, And the n-electrode 1 is connected to the lead 24 via the bonding wire 23.

[0004]

The conventional gallium nitride based compound semiconductor light emitting device shown in FIG.
In order to form on the crystal growth surface of the cladding layer 11,
A large substrate was required only for the portion 2. Also, the n-electrode 1
Since light was not emitted from the connection area portion with the n-GaN cladding layer 11, it was inefficient. Conventional light emitting devices are n-Ga
In the N-cladding layer 11, the current flows in the lateral direction toward the n-electrode 1, so that a spreading resistance is generated and the element resistance is large. Conventional gallium nitride-based compound semiconductor light-emitting devices are manufactured using AlxGayIn
1-x-yN (0 ≦ x, y ≦ 1, x + y ≦ 1) It is necessary to remove a part of the active layer 10 and the p-GaN cladding layer 9 and to form the transparent electrode 27 and the insulating film 28. Needed. The n-electrode 1 is formed on the n-GaN cladding layer 11, and requires a step of connecting to the lead 24 via the bonding wire 23 as shown in FIG. The step of chip formation is difficult due to the hard material of the sapphire substrate, which has led to a decrease in yield.

[0005]

The gallium nitride based compound semiconductor light emitting device of the present invention comprises an n-GaN cladding layer and the n-GaN cladding layer.
AlxGayIn1-x-yN formed on the cladding layer (0 ≦ x, y ≦ 1, x
+ y ≦ 1) an active layer made of a material, a p-GaN cladding layer formed on the active layer, a connection layer formed on the p-GaN cladding layer, and a p-GaN cladding layer formed on the p-GaN cladding layer. A conductive substrate, a first electrode formed on the conductive substrate,
a second electrode formed on a part of the n-GaN cladding layer. The conductive substrate is made of Si, G
e, GaP, GaAs or InP. Further, the connection layer is made of one of Au, Ag, Ni, In, and Ga. Further, the method for manufacturing a gallium nitride-based compound semiconductor light emitting device includes a step of forming a buffer layer on a substrate, a step of sequentially forming an n-GaN cladding layer, an active layer, and a P-GaN cladding layer on the buffer layer, Forming a layer on the P-GaN cladding layer, laminating a conductive substrate on the connection layer, forming a first electrode on the conductive substrate, the substrate and the buffer A step of removing a layer; and a step of forming a second electrode on a part of the n-GaN cladding layer.

As described above, according to the present invention, in the structure of the light emitting device, one of the two electrodes is formed on the conductive substrate, and the connection area of the electrode conventionally formed on the n-GaN cladding layer is reduced. Only the emission can be increased. Further, since the current flows in a direction perpendicular to the layer of the double heterostructure, the element resistance can be suppressed as compared with the conventional flow in the lateral direction in the n-GaN cladding layer. In the manufacture of light emitting devices,
By removing the hard sapphire substrate, it becomes easy to make a chip, and the yield can be improved.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments. FIG. 1 is a sectional view showing a schematic structure of an LED using the semiconductor light emitting device of the present invention. The semiconductor light emitting device is arranged on the lead 5 with the n-electrode 1 facing up, and n
The electrode 1 is connected to a lead 3 via a bonding wire 2. The p electrode 4 is directly connected to the lead 5 without using a bonding wire. The light emitting element and a part of the lead are covered with the transparent resin 6. FIG. 2 is a sectional view showing a schematic structure of the semiconductor light emitting device in the first embodiment. The semiconductor light emitting element is a p-electrode 4, GaAs in order from the bottom.
Conductive substrate 7, Au connection layer 8, p-GaN cladding layer 9, InGaN
It comprises an active layer 10, an n-GaN cladding layer 11, and an n-electrode 1 formed on a part of the n-GaN cladding layer 11. In the first embodiment, the n-electrode 1 and the p-electrode 4 are formed vertically so as to sandwich the double heterostructure and the GaAs conductive substrate 7 therebetween. For this reason, the chip size can be reduced by the area (12 in FIG. 12) conventionally required to connect the n-electrode 1 to the crystal growth surface. 1 square of 350 μm on each side
Since the side can be reduced to 200 μm, the number of chips that can be obtained from a 2-inch wafer can be increased from about 16,000 to about 49,000. If the chip size is not changed, the light emitting area can be widened. FIG. 3 shows the IV characteristics of the semiconductor light emitting device in the first embodiment. The semiconductor light emitting device in the first embodiment showed a voltage drop of about 0.3 V at an injection current of 20 mA as compared with the conventional light emitting device. This is considered to be due to the fact that the element resistance was reduced due to the vertical flow of current in the double heterostructure. In this embodiment, GaAs is used for the conductive substrate 7, but any one of Si, Ge, GaP, and InP can be used instead, and the connection layer 8 can be made of Ga, In, Ni, or Ag instead of Au. Can be used.

Next, a manufacturing process of the semiconductor light emitting device shown in the first embodiment will be described with reference to FIGS. 2, 4 and 5. FIG. FIG.
In the GaN buffer layer 13 on the sapphire substrate 14,
To form An n-GaN cladding layer 11 is formed on the GaN buffer layer 13 by molecular beam epitaxy (MBE).
A double hetero structure comprising the N active layer 10 and the p-GaN cladding layer 9 is formed. Then, the Au connection layer 8 is p-
It is formed on the GaN cladding layer 9 (FIG. 5). The thickness of the Au connection layer 8 is set to 10 nm or less. Au GaAs conductive substrate 7
Bonding is performed by performing annealing at 700 ° C. for 1 hour in a nitrogen gas atmosphere while being in close contact with the connection layer 8 in a pressurized state. Au used for the connection layer 8 is a p-GaN cladding layer 9.
And the deposition of Ga from the GaAs conductive substrate 7 is promoted. The combination of the deposited Ga and the connection layer Au causes the GaAs conductive substrate 7 to adhere to the double heterostructure. The thickness of the GaAs conductive substrate 7 is 50
Set in the range of μm to 100 μm. Sapphire substrate 14
Is polished to a thickness of about 10 μm, and RIE (Reactive Ion Etchin
Complete removal using method g). GaN buffer layer 13 is also RIE
Remove completely by method. Sapphire substrate 14 and Ga
N-GaN cladding layer 1 exposed by removing N buffer layer 13
An n-electrode 1 made of Ni is formed on a part of the first electrode 1 (FIG. 2).
Note that Ti, Al or AuGe can be used for the n-electrode 1. P electrode 4 made of AuZn on GaAs conductive substrate 7
To form Both p-electrode and n-electrode are in nitrogen atmosphere 500
An ohmic electrode is formed by annealing at 20 ° C. for 20 seconds. By removing the sapphire substrate 14 and forming the GaAs conductive substrate 7 in the manufacturing process of the first embodiment,
The step of chip formation is facilitated, and the yield can be improved. FIG. 6 is a sectional view showing a light emitting device according to the second embodiment of the present invention. In the figure, n electrode 1, p electrode 4, Ga
As conductive substrate 7, Au connection layer 8, p-GaN cladding layer 9, InG
Since the aN active layer 10 and the n-GaN cladding layer 11 have the same structure as in the first embodiment, description thereof will be omitted. In this embodiment,
It differs from the first embodiment in that a Pt film 15 and an Au connection layer 16 are formed between the Au connection layer 8 and the GaAs conductive substrate 7.
After the formation of the Au connection layer 8, the Pt film 15 is formed by vapor deposition on the Au connection layer 8, and the Au connection layer 16 is formed by vapor deposition on the Pt film 15. Next, the GaAs conductive substrate 7 is bonded to the Au connection layer 16 by being annealed at 700 ° C. for 1 hour in a nitrogen gas atmosphere while being closely adhered to the Au connection layer 16. In the present embodiment, Au is used for the connection layers 8 and 16, but any of Ga, Ni, In, and Ag can be used instead. The connection layers 8 and 16 are not necessarily a uniform thin film but may be in a cluster shape or some pattern shape. The Pt film 15 is made of Ni, Pd,
W, Mo, Ti may be used. The Pt film 15 has Au connection layers 8 and 16
Can be stabilized against heat.

FIG. 7 is a sectional view showing a light emitting device according to a third embodiment of the present invention. In the figure, an n-electrode 1, a p-electrode 4, a conductive substrate 7, an Au connection layer 8, a p-GaN cladding layer 9, an InGaN active layer 10, and an n-GaN cladding layer 11 have the same structure as in the first embodiment. Therefore, the description is omitted. In this embodiment, a p-AlGaInP layer 17 is formed between the Au connection layer 8 and the GaAs conductive substrate 7, and a p-InGaN layer 18 is formed between the Au connection layer 8 and the p-GaN cladding layer 9. This is different from the first embodiment. The p-InGaN layer 18 is crystal-grown on the p-GaN cladding layer 9, the Au connection layer 8 is deposited on the p-InGaN layer 18,
The -AlGaInP layer 17 is grown on the GaAs conductive substrate 7. Then, while the p-AlGaInP layer 17 and the Au connection layer 8 are brought into close contact with each other in a pressurized state, annealing is performed at 700 ° C. for 1 hour in a nitrogen gas atmosphere to bond them together. Au connection layer 8
Promotes the precipitation of Ga and In from the p-AlGaInP layer 17 and the p-InGaN layer 18. Therefore, the bonding of the conductive substrate 7 and the double hetero structure portion can be easily performed. p-AlGaInP
Layer 17 is made of InGaAs, InGaP, AlGaAs, AlGaAsP, InGaAsP, AlGaP.
InP and p-InGaAs can also be used, and the p-InGaN layer 18 can also use AlGaN, InGaN, AlGaInN, and p-AlGaN.

FIG. 8 is a sectional view showing a light emitting device according to a fourth embodiment of the present invention. In the figure, n electrode 1, p electrode 4, p-
Since the GaN cladding layer 9, the InGaN active layer 10, and the n-GaN cladding layer 11 have the same structure as in the first embodiment, the description is omitted. In this embodiment, the GaAs conductive substrate 7 is replaced with p-Si
The point of using the conductive substrate 20 and instead of the Au connection layer 8
It differs from the first embodiment in that a super lattice 19 made of p-GaP / p-GaAs is used. The p-Si conductive substrate 20 is bonded to the super lattice 19 by being annealed at 700 ° C. for 1 hour in a nitrogen gas atmosphere while being brought into close contact with the super lattice 19 in a pressurized state. When the Au connection layer 8 is used in bonding the p-Si conductive substrate 20 to the double hetero structure, p-Ga
Ga is deposited only from the N cladding layer, and bonding becomes difficult. The super lattice 19 is formed by crystal growth of a single atomic layer from the p-GaN cladding layer 9 on the p-GaN cladding layer 9. It serves to reduce the difference between the constants. If the super lattice 19 is used instead of the Au connection layer 8, p-Si can be used for the conductive substrate. The super lattice 19 is composed of about 20 pairs of p-GaP / p-GaAs layers. The p-GaP layer is thicker as the p-SiP
It is formed to be thin on the s conductive substrate 7 side. Conversely p
The -GaAs layer is formed to be thinner near the p-Si conductive substrate 20 and to be thicker on the GaAs conductive substrate 7 side.

FIG. 9 is a sectional view showing a light emitting device according to a fifth embodiment of the present invention. In the figure, n electrode 1, p electrode 4, Au
Connection layer 8, p-GaN cladding layer 9, InGaN active layer 10, n-Ga
Since the N clad layer 11 has the same structure as that of the first embodiment, the description is omitted. In this embodiment, the Au connection layer 8 and the p-GaN
DBR consisting of 15 pairs of In0.1GaN / AlN between cladding layer 9
(Distributed Bragg Reflector) layer 21 is formed. The thickness of the In0.1GaN of the DBR layer is 0.045 μm, and the AlN is set to 0.052 μm. The conductive substrate 22 uses Si. Since the DBR layer 21 has a light reflectance of 90%, if it is formed between the p-GaN cladding layer 9 and the Au connection layer 8, the substrate absorption of light can be prevented. DBR layer 21 is A
It can be formed between the u connection layer 8 and the Si conductive substrate 22. FIG. 10 is a top view of a light emitting device according to an embodiment of the present invention. In the figure, reference numeral 11 denotes an n-GaN cladding layer, and the n-electrode 1 is formed at the center of the n-GaN cladding layer 1. The n-electrode 1 is not limited to being located at the center on the n-GaN cladding layer 11, but can be arranged at a position other than the center.

[0012]

According to the structure of the gallium nitride based compound semiconductor light emitting device of the present invention, the effective light emitting area ratio and the chip yield can be increased. Due to the structure of the light emitting element, the current flows in the direction perpendicular to the layer of the double heterostructure, so that the element resistance can be suppressed as compared with the conventional flow in the lateral direction. Adhesion can be improved by interposing the connection layer on the double heterostructure and the conductive substrate. By removing the sapphire substrate and forming the conductive substrate in the manufacturing process of the gallium nitride-based compound semiconductor light-emitting device, it becomes easy to make a chip and the yield can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an LED using a semiconductor light emitting device according to an embodiment of the present invention;

FIG. 2 is a sectional view showing a semiconductor light emitting device according to a first embodiment of the present invention;

FIG. 3 is a diagram showing IV characteristics of a semiconductor light emitting device according to an embodiment of the present invention and a conventional light emitting device.

FIG. 4 is a sectional view showing a manufacturing process of the semiconductor light emitting device according to the first embodiment of the present invention;

FIG. 5 is a sectional view showing a manufacturing process of the semiconductor light emitting device according to the first embodiment of the present invention;

FIG. 6 is a sectional view showing a semiconductor light emitting device according to a second embodiment of the present invention;

FIG. 7 is a sectional view showing a semiconductor light emitting device according to a third embodiment of the present invention;

FIG. 8 is a sectional view showing a semiconductor light emitting device according to a fourth embodiment of the present invention;

FIG. 9 is a sectional view showing a semiconductor light emitting device according to a fifth embodiment of the present invention;

FIG. 10 is a top view of a semiconductor light emitting device according to an embodiment of the present invention;

FIG. 11 is a cross-sectional view showing an LED using a conventional gallium nitride-based compound semiconductor light emitting device.

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

[Explanation of symbols]

1 ... n electrode, 2, 23, 25 ... bonding wire,
3, 5, 24, 26 lead, 4 p electrode, 6 transparent resin, 7 GaAs conductive substrate, 8, 16 Au connection layer, 9 p-GaN
Cladding layer, 10 ... AlxGayIn1-x-yN (0 ≦ x, y ≦ 1, x + y ≦ 1)
Active layer, 11 n-GaN cladding layer, 12 parts required for forming n electrode, 13 GaN buffer layer, 14 sapphire substrate, 15 Pt film, 17 p-AlGaInP layer, 18 InGaN
Layer, 19 ... super lattice, 20 ... p-Si conductive substrate,
21: DBR layer, 22: Si conductive substrate, 27: transparent electrode,
28 ... Insulating film.

Claims (6)

[Claims] 1. An n-GaN cladding layer, and an active layer made of AlxGayIn1-x-yN (0 ≦ x, y ≦ 1, x + y ≦ 1) formed on the n-GaN cladding layer; A p-GaN cladding layer formed on the active layer, a connection layer formed on the p-GaN cladding layer, a conductive substrate formed on the connection layer, and formed on the conductive substrate A gallium nitride-based compound semiconductor light emitting device, comprising: a first electrode formed as described above; and a second electrode formed on a part of the n-GaN cladding layer. 2. The gallium nitride-based compound semiconductor light-emitting device according to claim 1, wherein said conductive substrate is any one of Si, Ge, GaP, GaAs and InP. 3. The gallium nitride-based compound semiconductor light-emitting device according to claim 1, wherein said connection layer is made of one of Au, Ag, Ni, In, and Ga. 4. A step of forming a buffer layer on a substrate, and forming an n-GaN cladding layer and AlxGayIn1-x-yN (0
≦ x, y ≦ 1, x + y ≦ 1) a step of sequentially forming an active layer made of a material and a P-GaN cladding layer; a step of forming a connection layer on the P-GaN cladding layer; and Laminating a conductive substrate on, a step of forming a first electrode on the conductive substrate, a step of removing the substrate and the buffer layer, and a part on the n-GaN cladding layer Forming a second electrode. A method for manufacturing a gallium nitride-based compound semiconductor light emitting device, comprising: 5. An n-GaN cladding layer, and an active layer made of AlxGayIn1-x-yN (0 ≦ x, y ≦ 1, x + y ≦ 1) formed on the n-GaN cladding layer; A p-GaN cladding layer formed on the active layer, a first connection layer formed on the p-GaN cladding layer, a refractory metal film formed on the first connection layer, A second connection layer formed on the refractory metal film, a conductive substrate formed on the second connection layer, a first electrode formed on the conductive substrate, and the n -GaN
A gallium nitride-based compound semiconductor light emitting device, comprising: a second electrode formed on a part of the cladding layer. 6. An n-GaN cladding layer, and an active layer made of AlxGayIn1-x-yN (0 ≦ x, y ≦ 1, x + y ≦ 1) material formed on the n-GaN cladding layer, A p-GaN cladding layer formed on the active layer, a light reflection layer formed on the p-GaN cladding layer, a connection layer formed on the light reflection layer, and a light reflection layer formed on the connection layer. A conductive substrate, a first electrode formed on the conductive substrate, and a second electrode formed on a part of the n-GaN cladding layer. Gallium nitride based compound semiconductor light emitting device.