JPH11220171A - Gallium nitride compound semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gallium nitride compound semiconductor device, having large luminous intensity and a long lifetime. SOLUTION: An electrode connected to a contact layer 107 is formed of a first metal layer 108 connected with the contact layer 107 on the p-type semiconductor side and consisting of silver (Ag), etc., and a second metal layer 110 covering the surface of the first metal layer 108 and the surface of the contact layer 107 which is not covered with the first metal layer 108 is formed. The value of contact resistance per unit area to the contact layer 107 of the second metal layer 110 is made larger than that of the first metal layer 108. Junction strength to the contact layer 107 is reinforced by forming the first metal layer 108 or the second metal layer 110 into a multilayered structure by plural kinds of metals. A light-emitting element having high reflection efficiency of light by the electrode and long lifetime is obtained by these means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flip-chip type light emitting device in which a gallium nitride-based compound semiconductor layer is stacked on a substrate.

[0002]

2. Description of the Related Art FIG.
1 illustrates a cross-sectional view of a flip chip light emitting device 300 according to 0562. 301 is a sapphire substrate, 302 is n
GaN layer, 303 is a p-type GaN layer, 304 is
A positive electrode 305 is a negative electrode. In the flip-chip type light emitting element, light emitted at the interface between the n-type GaN layer 302 and the p-type GaN layer 303 is reflected by the positive electrode 304 formed on the p-type GaN layer 303, and the sapphire substrate 301 For observation through, the positive electrode 304 is formed relatively large. As a metal layer used for the positive electrode 304 formed on the p-type GaN layer 303, a metal such as aluminum (Al) is known to be excellent in light reflection efficiency. Among the types of metals that are excellent in light reflection efficiency, when they are used for electrodes, there are those that easily cause migration, for example, metals such as aluminum.

[0003]

As described above, when the metal used for the positive electrode 304 causes migration, the metal constituting the positive electrode 304 is attracted to the negative electrode 305 as ions, and This causes a problem that the light emission intensity is reduced due to the disturbance, the positive electrode 304 and the n-type GaN layer 302 are short-circuited due to migration, and the life is shortened. Therefore, for example, as shown in FIG. 3, the positive electrode 304 formed on the p-type GaN layer 303 and the p-type Ga
By increasing the distance D from the N layer 303, the time until a short circuit is extended, and as a result, a method of extending the life can be considered. However, as described above, for the flip-chip type light emitting element, the size of the positive electrode 304 on the p-type GaN layer 303 = the light emitting area, and increasing the distance D reduces the size of the positive electrode. If it is maintained, the chip size increases and the production efficiency decreases, and if the size of the positive electrode is reduced, the amount of light leaking from the gap D of the p-type GaN layer 303 is accordingly increased. As a result, there is a problem that the light reflection efficiency is reduced and the light emission efficiency is reduced. In addition, it is impossible to prevent the emission intensity from being reduced due to the disturbance of the electrode layer.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a gallium nitride-based compound semiconductor device having a large emission intensity and a long life.

[0005]

A first means for solving the above problems is a flip chip type light emitting device in which a layer made of a gallium nitride-based compound semiconductor is laminated on a substrate. First connecting to the contact layer of
And a second metal layer covering at least the side surface of the first metal layer and the surface of the contact layer not covered with the first metal layer to form an electrode connected to the contact layer. is there. Note that the second metal layer includes a case where the second metal layer covers the periphery of the surface of the first metal layer and the exposed portion of the contact layer, and a case where the second metal layer covers the entire surface of the first metal layer and the exposed portion of the contact layer. . The second means is:
In the above first means, the value of the contact resistance per unit area of the second metal layer with respect to the contact layer is made larger than the value of the first metal layer. Further, the third means is the first means or the second means,
Is to form a multi-layered structure using a plurality of types of metals. The fourth means is:
In any one of the first to third means, the first metal layer is formed of silver (Ag). Further, a fifth means is the device according to any one of the first to fourth means, wherein the second metal layer is formed of vanadium (V) and aluminum (Al) or titanium (Ti) and gold (Au). ). With these means, the above-mentioned problems can be solved.

[0006]

FIG. 1 shows the first metal layer 108.
FIG. 1 is a cross-sectional view of a flip-chip type light emitting device 100 according to the present invention using silver (Ag). In the element 100, migration does not occur because the first metal layer 108 is covered with the second metal layer 110. Therefore, this element 1
00 has a long life. Further, in the present element 100, since the migration D does not occur, the width D can be reduced, so that the first metal layer 108 can be widened, and a metal having excellent spectral reflection efficiency can be provided on the first metal layer 108 over a large area. Can be used over. Therefore, the emission intensity can be improved. Further, in the present element 100, since light is reflected by the second metal layer 110 even in the portion having the width D, the contact layer 1
07 hardly leaks out, so that the emission intensity can be further improved. In addition, the present element 100
Then, since the contact resistance of the second metal layer 110 to the contact layer 107 at the portion of the width D is larger than the contact resistance of the first metal layer 108 to the contact layer 107, most of the current flows in the portion of the width D. Contact layer 1 without passing through
07 and the metal layer 108. For this reason,
The active layer immediately above the metal layer 108, which uses a metal having excellent light reflection efficiency over a wide area, emits light, and thus has a high emission intensity. Further, in the present element 100, since the portion having the width D is narrow, a strong bonding strength is required when the contact layer 107 and the second metal layer 110 are bonded. However, as shown in FIG. When the layer 110 has a multilayer structure, strong bonding strength can be obtained. Thereby, the present element 1
00 can be a long-life element in which migration does not occur. The second metal layer 110 also has an effect of preventing oxygen and moisture from entering the first metal layer 108 and preventing the first metal layer 108 from corroding.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on specific embodiments. FIG. 1 shows that the first metal layer has silver (Ag).
Chip type light emitting device 10 using the present invention
0 is a sectional view. 101 is a sapphire substrate, 102
Is an AlN buffer layer, 103 is an n-type GaN layer, 1
04 is an n-type GaN cladding layer, 105 is an active layer,
106 is a p-type AlGaN cladding layer, and 107 is a p-type AlGaN cladding layer.
The type GaN contact layer 108 is a first metal layer constituting a part of the positive electrode, and is formed of silver (Ag). Reference numeral 109 denotes a negative electrode, and 110 denotes a second metal layer forming a part of the positive electrode. That is, the second metal layer 110 is composed of the metal layer 111 formed of vanadium (V) and the metal layer 112 formed of aluminum (Al), and has a width D that can sufficiently secure the bonding strength. It is in contact with contact layer 107. Since the element 100 uses silver (Ag), which has not been used as a member of the conventional flip-chip type positive electrode, for the first metal layer, the contact resistance to the contact layer 107 is small, and FIG. Since the reflection efficiency of the light upward to 1 is very good, it is a great feature that the light emission intensity is remarkably excellent. In the case of the above-described embodiment using silver (Ag) for the first metal layer 108, the first metal layer 10
8 is most preferably in the range of about 200 ° to 1 μm. If it is thinner than this, the reflection efficiency of light decreases. If it is thicker, the second metal layer 110 completely covers the side surface of the first metal layer 108. It is difficult to cover the surface, and the production cost is inferior.

FIG. 2 is a cross-sectional view of a flip-chip type light emitting device 200 according to the present invention in which a multilayer structure is also used for the first metal layer. 201 is a sapphire substrate, 202 is
AlN buffer layer, 203 is an n-type GaN layer, 204
Is an n-type GaN cladding layer, 205 is an active layer, 20
6 is a p-type AlGaN cladding layer, 207 is a p-type GaN contact layer, 208 is a first metal layer constituting a part of the positive electrode, and is a 3000 mm thick silver (Ag) layer 208A; Nickel (Ni) layer 208 having a thickness of 1000 °
B, a multilayer structure composed of a titanium (Ti) layer 208C having a thickness of 1000 °. 209 is a negative electrode, and 210 is a second metal layer forming a part of the positive electrode. That is, the second metal layer 210 is made of titanium (Ti).
And a metal layer 21 with a thickness of 1.5 μm and made of gold (Au).
2 and is in contact with the contact layer 207 with a width D sufficient to ensure sufficient bonding strength.
In this element 200, the first metal layer has a silver (Ag) layer 208A having a thickness of 3000 .ANG.
i) Layer 208B, titanium (Ti) layer 2 having a thickness of 1000 °
08C, the contact resistance with respect to the contact layer 207 is low, and the first metal layer 208C and the second metal layer 211 are made of the same metal, so that the first metal layer and the second metal layer 211 are formed of the same metal. It is excellent in that the bonding strength with the metal layer is strong.

In the above embodiment, silver (Ag) is used for the metal layer which is in surface contact with the contact layer of the first metal layer, but the metal used for this layer is nickel (Ni),
It may be cobalt (Co), gold (Au), platinum (Pt), or an alloy thereof. Further, in the above embodiment, vanadium (V) and titanium (Ti) are used for the metal layer which is in surface contact with the contact layer of the second metal layer, but the metal used for this layer is chromium (Cr), Niobium (Nb), zinc (Zn), tantalum (Ta), molybdenum (Mo), tungsten (W),
It may be hafnium (Hf) or an alloy thereof, and may be the same as the negative electrode (109, 209) generally attached to the n-type GaN layer (103, 203). Further, in the above embodiment, the second metal layer is
While completely covering the first metal layer, the second metal layer
The first metal layer may not be completely covered, and at least the bottom surface of the contact layer not covered by the first metal layer and the first
What is necessary is just to cover the side surface of the metal layer.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a flip-chip type light emitting device according to the present invention using silver (Ag) for a first metal layer.

FIG. 2 is a cross-sectional view of a flip-chip type light emitting device according to the present invention in which a multilayer structure is also used for a first metal layer.

FIG. 3 is a cross-sectional view of a flip-chip type light emitting device according to a conventional technique using silver (Ag) for a first metal layer.

[Explanation of symbols]

 101, 201, 301: sapphire substrate 102, 202: AlN buffer layer 103, 203, 302: n-type GaN layer 104, 204: n-type GaN cladding layer 105, 205: active layer 106, 206: p-type AlGaN Cladding layers 107, 207: p-type GaN contact layer 108, 208: first metal layer constituting a part of the positive electrode 303: p-type GaN layer 304: positive electrode 109, 209, 305: negative electrode 110; 210: second metal layer constituting a part of the positive electrode

Claims (5)

[Claims] A first metal layer connected to a contact layer on a p-type semiconductor side in a flip-chip type light-emitting element in which a layer made of a gallium nitride-based compound semiconductor is laminated on a substrate; A gallium nitride-based compound semiconductor, wherein an electrode connected to the contact layer is constituted by at least a side surface of the layer and a second metal layer covering a surface of the contact layer not covered by the first metal layer. element. 2. The value of the contact resistance per unit area of the second metal layer with respect to the contact layer is larger than the value of the contact resistance per unit area of the first metal layer with respect to the contact layer. The gallium nitride-based compound semiconductor device according to claim 1, wherein: 3. The gallium nitride according to claim 1, wherein the first metal layer or the second metal layer has a multilayer structure made of a plurality of kinds of metals. -Based compound semiconductor devices. 4. The gallium nitride based compound semiconductor device according to claim 1, wherein the first metal layer is formed of silver (Ag). 5. The method according to claim 1, wherein the second metal layer is formed of vanadium (V).
And aluminum (Al) or titanium (Ti) and gold (A
The gallium nitride-based compound semiconductor device according to any one of claims 1 to 4, wherein the gallium nitride-based compound semiconductor device is formed of u).