JP2000315817A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance translucence by providing an electrode including a carbon film on a specified semiconductor layer having conductivity thereby suppressing occurrence of surge breakdown and defect and decreasing electric resistance. SOLUTION: A buffer layer 2 of GaN and an Si doped n-type clad layer 3 of AlxGa1-x-yInyN (0<=x<=1, 0<=y<=1, 0<=x+y<=1) are formed on a sapphire substrate 1. An undoped light emitting layer 4 of In0.2Ga0.8N and an Mg doped p-type clad layer 5 of AlxGa1-x-yInyN are formed on a partial region of the clad layer. A negative electrode 6 of graphite film is formed on the exposed n-type clad layer 3 and a positive electrode 7 of graphite film is formed on the p-type clad layer 5. Consequently, breakdown, e.g. short circuit, is retarded, resistivity of electrode is decreased and emission efficiency can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a compound represented by the general formula: Al _x G
a _1-xy In _y N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y
The present invention relates to a semiconductor device comprising a nitride compound represented by ≦ 1).

[0002]

2. Description of the Related Art Hitherto, Ni, A have been formed on a semiconductor layer made of a p-type nitride compound to which a group 2 element has been added.
A technique of forming a film made of u or an alloy thereof to form an electrode is known.

Conventionally, among semiconductor devices made of a nitride compound, a light emitting diode (LED) having a structure in which light is extracted from a surface on which an electrode is formed is disclosed in Japanese Patent Application Laid-Open No. H11-157300. 7-1066
As disclosed in JP-A-33-33, there is known a technique in which Ni, Au, or the like is formed very thinly to form an electrode, thereby enhancing the translucency of the electrode.

[0004]

SUMMARY OF THE INVENTION However, Ni, Au
Alternatively, when a film made of an alloy thereof is formed on a semiconductor layer made of a nitride-based compound and used as an electrode, a short circuit or the like occurs when a surge or the like is applied to the semiconductor device, and the semiconductor device is destroyed or There is a problem that a defect of the semiconductor device occurs.

In an LED having a structure in which light is extracted from a surface on which an electrode is formed, when a very thin Ni or Au or the like is used as an electrode, a metal wiring connected to the electrode is formed only at one point of the electrode. Since the connection is not made, the electric resistance of the electrode is increased by reducing the thickness of the electrode with respect to the current flowing in the electrode in the lateral direction, and the current can be uniformly injected into the semiconductor layer on the surface on which the electrode is formed. There was a problem that it became difficult.

In view of the above problems, the present invention is to provide a semiconductor device made of a nitride-based compound having an electrode which is less likely to be broken or defective due to a surge or the like, has a sufficiently small electric resistance, and has an improved translucency. It is.

[0007]

In order to solve the above-mentioned problems, a semiconductor device according to the present invention comprises a conductive Al _x Ga _1.
-xy In _y N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦
It has a semiconductor layer made of 1) and an electrode formed on the semiconductor layer, and the electrode contains a film made of carbon.

According to this configuration, since the electrode made of the carbon film is formed on the semiconductor layer, breakage such as short-circuit is less likely to occur than in the conventional semiconductor device, and the light transmitting property is improved and the electrode is formed. Since the thickness can be increased, the electric resistance in the lateral direction can be reduced.

In the semiconductor device according to the present invention, the film made of carbon is a film made of graphite.

[0010] With this configuration, since the electrode made of a graphite film is formed on the semiconductor layer, breakage such as short-circuit is less likely to occur than in the conventional semiconductor device, and it can be formed at a low cost.

In the semiconductor device according to the present invention, the film made of carbon is a film made of a diamond crystal.

According to this structure, since the electrode made of the diamond crystal film is formed on the semiconductor layer, breakage such as short-circuit is less likely to occur and the light transmission is improved as compared with the conventional semiconductor device.

According to the semiconductor device of the present invention, the film made of carbon is a film made of amorphous diamond.

According to this structure, since a film made of amorphous diamond is formed on the semiconductor layer, breakage such as short-circuit is less likely to occur than in the conventional semiconductor device, and transparency is higher than graphite. The luminous efficiency can be improved and the cost can be lower than that of a diamond crystal.

In the semiconductor device according to the present invention, the film made of carbon is a film to which a Group 3 element or a Group 5 element is added.

According to this structure, since a film made of carbon to which a group III element is added for the n-type electrode and a group V element to which the p-type element is added is used on the semiconductor layer, the conductivity is improved. Thus, a current can be made to flow uniformly over the entire surface of the electrode.

In the semiconductor device of the present invention, the element belonging to Group 3 is boron.

According to this configuration, since boron having the lowest acceptor level with respect to diamond is used as the group III element, the electrical resistivity of the membrane electrode can be further reduced.

According to the semiconductor device of the present invention, the element belonging to Group 5 is phosphorus.

According to this configuration, since phosphorus is used as the group V element, the electrical resistivity of the membrane electrode can be further reduced.

According to the semiconductor device of the present invention, the electrode has a structure in which a film made of a conductive oxide is formed on a film made of carbon from the semiconductor layer side.

According to this structure, since the film made of carbon is formed directly on the semiconductor layer, breakdown such as short-circuit is less likely to occur than in the conventional semiconductor device, and the electric conductivity is smaller than that of the film made of carbon. Since the film made of the conductive oxide is formed, the current can flow more uniformly over the entire surface of the electrode.

According to the semiconductor device of the present invention, the conductive oxide is indium tin oxide.

With this configuration, since indium tin oxide having lower electric resistance than carbon is used, current can be more uniformly applied to the entire surface of the electrode.

In the semiconductor device according to the present invention, the electrode has a structure in which a film made of conductive nitride is formed on a film made of carbon from the semiconductor layer side.

According to this structure, since the film made of carbon is formed directly on the semiconductor layer, breakdown such as short-circuit is less likely to occur than in the conventional semiconductor device, and a conductive material having lower electric resistance than the film made of carbon. Since the film made of the crystalline nitride is formed, the current can be more uniformly flowed over the entire surface of the electrode.

In the semiconductor device according to the present invention, the electrode has a structure in which a metal film is formed on the carbon film from the semiconductor layer side.

According to this configuration, since the metal film is formed on the film made of carbon, it is easy to wire-bond the electrodes with gold or the like or to fix them with gold-tin solder or the like.

According to the semiconductor device of the present invention, at least one kind of a metal belonging to Group 3 such as Al, Ga, and In is used as the metal film.

According to this configuration, since the group III element diffuses into the undoped amorphous diamond film and acts as an impurity, the contact resistance between the undoped amorphous diamond film and the metal film can be reduced.

According to the semiconductor device of the present invention, Ti is used as the metal film in such a configuration.

According to this configuration, since Ti having good adhesion to diamond is used, peeling of the metal film can be suppressed.

According to the semiconductor device of the present invention, Cr, Ni, Cu, Mo, Pd, W,
At least one metal of Au and Pt is used.

According to this configuration, Cr having a large work function,
Since Ni, Cu, Mo, Pd, W, Au or Pt is used, the contact resistance between the semiconductor layer and the metal film can be reduced.

According to the semiconductor device of the present invention, the semiconductor layer is a layer to which a group 2 element is added.

According to this configuration, the contact resistance between the semiconductor layer and the film made of carbon can be reduced.

According to the semiconductor device of the present invention, in the above structure, the group 2 element is Mg and the concentration of Mg is 2 × 10
It is not less than ¹⁸ cm ^{-3 and not} more than 1 × 10 ²¹ cm ^-3 .

According to this structure, the contact resistance between the semiconductor layer and the film made of carbon can be reduced.

The semiconductor device according to the present invention has conductivity and Al _x Ga _{1 -xy} In _y N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1,
A substrate comprising 0 ≦ x + y ≦ 1) and an electrode formed on the substrate, wherein the electrode includes a film made of carbon.

According to this structure, since the film made of carbon is formed on the substrate, it is less likely to be broken such as a short circuit as compared with a conventional semiconductor device, and can be used as a substrate electrode.

[0041]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) A nitride-based compound semiconductor device according to a first embodiment of the present invention, as shown in FIG.
nm of the buffer layer 2 and the Si n-type cladding layer 3 having a thickness of 2.0μm made of GaN having a conductivity is doped n-type is formed, undoped In _0.2 on a region of a portion of the cladding layer 3 A light emitting layer 4 of Ga _0.8 N having a thickness of 20 nm and a p-type cladding layer 5 of 0.5 μm thick made of GaN doped with Mg and having p-type conductivity are formed.
On the exposed n-type cladding layer 3, a negative electrode 6 made of a graphite film having a thickness of 50 nm is formed, and on the p-type cladding layer 5, a thickness of 50 nm made of a graphite film is formed.
Of the positive electrode 7 is formed. That is, a light emitting diode (LED) made of nitride is formed.

In the method of forming this structure,
Each layer from the buffer layer 2 to the p-type clad layer 5 is formed by an organic vapor phase metal epitaxial growth (hereinafter referred to as MOVPE) method.

As a method of forming the light emitting layer 4 and the p-type cladding layer 5 on a part of the n-type cladding layer 3, the n-type cladding layer 3, the light-emitting layer 4 and a part of the p-type cladding layer 5 are formed. Dry etching is performed from above the p-type cladding layer 5 to the middle of the n-type cladding layer 3. Further, the negative electrode 6 and the positive electrode 7 using a graphite film are formed by sputtering.

With this configuration, since the positive electrode 7 made of a graphite film is formed on the p-type cladding layer 5, breakage such as short-circuit is less likely to occur than in a conventional semiconductor device.

The LED according to the first embodiment (hereinafter referred to as sample A) was subjected to the following destructive test. For comparison, a conventional LED in which titanium having a thickness of 50 nm and gold having a thickness of 100 nm are sequentially formed on the negative electrode 6 and nickel having a thickness of 50 nm and gold having a thickness of 100 nm are sequentially formed on the positive electrode 7. (Hereinafter referred to as Sample B), a destructive test was also performed. This breakdown test was performed by applying a reverse voltage to the LED, examining the breakdown voltage characteristics, and then applying a forward voltage to the LED to examine the element characteristics of the LED. That is, a metal needle is brought into contact with each of the negative electrode 6 and the positive electrode 7, the needle is connected to a power source, the positive electrode 7 is grounded, and a positive voltage is applied to the negative electrode 6 until a reverse breakdown phenomenon occurs. After application, the negative electrode 6 is grounded and the positive electrode 7
By applying a positive voltage.

The reverse breakdown voltage of both samples A and B was about 100V. However, when a forward voltage was applied after the reverse breakdown occurred, sample A emitted light and operated normally as an LED, whereas
Sample B did not emit light due to a short circuit. The sample B caused a short circuit because the metal forming the negative electrode 6 and the positive electrode 7 was changed to the n-type cladding layer 3, the light-emitting layer 4, and the p-type cladding layer when a large current flowed due to the reverse breakdown phenomenon. It is considered that this was due to the diffusion in the penetration defect existing in 5. On the other hand, it is considered that the reason why the sample A operated normally was that the graphite constituting the negative electrode 6 and the positive electrode 7 was unlikely to diffuse through the penetration defect.

In the first embodiment, the reverse voltage is statically applied. However, the same applies to the case where the voltage is applied momentarily like a surge or the case where the forward voltage is applied. It has been found that the LED of the present invention is less likely to break, such as a short circuit, than the conventional LED.

In the first embodiment, graphite is used for the negative electrode 6 and the positive electrode 7. However, in addition to graphite, a conductive material made of other carbon such as single crystal diamond, polycrystalline diamond, amorphous diamond and the like is used. The same effect can be obtained by using a conductive material. In addition, impurities such as p, e.g.
Group 3 elements such as boron and 5
By adding a group element, conductivity can be improved and electric resistance can be reduced.

(Embodiment 2) A nitride-based compound semiconductor device according to a second embodiment of the present invention is formed on one main surface of a Si-doped n-type GaN substrate 8 as shown in FIG. , S
a 2.0 μm thick n-type cladding layer 3 made of GaN doped with i and n-type conductivity; a 20 nm thick light emitting layer 4 made of undoped In _0.2 Ga _0.8 N;
A 0.5 μm-thick p-type cladding layer 5 made of GaN doped with g and having p-type conductivity is sequentially formed, and another 50 nm-thick titanium layer is formed on the other main surface of the n-type GaN substrate 8. And a gold electrode having a thickness of 100 nm are sequentially formed, and a positive electrode 7 including a carbon film is formed on the p-type cladding layer 5. That is, a light emitting diode (LED) made of nitride is formed.

Hereinafter, the LE according to the second embodiment will be described.
An example using a film in which the shape and crystallinity of carbon are changed and an ITO film as the positive electrode 7 of D will be described.

(Embodiment 1) Positive electrode 7 according to Embodiment 1
For this, a film made of undoped amorphous diamond, that is, an undoped amorphous diamond film is used. This undoped amorphous diamond film is formed by sputtering. Less than,
The LED according to this example is referred to as sample C.

With this configuration, since the positive electrode 7 made of an undoped amorphous diamond film is formed on the p-type cladding layer 5, breakage such as short-circuit is less likely to occur than in a conventional semiconductor device.

Further, with this configuration, the p-type cladding layer 5 is formed.
Since the positive electrode 7 made of an undoped amorphous diamond film having higher transparency than the graphite film is formed thereon, the luminous efficiency can be improved as compared with the semiconductor device according to the first embodiment. .

(Embodiment 2) Positive electrode 7 according to Embodiment 2
A film made of an amorphous diamond doped with a group 3 element boron, that is, a p-type amorphous diamond film having good conductivity is used. The positive electrode 7 using the boron-doped amorphous diamond film is formed by sputtering. Hereinafter, the LED according to this example is referred to as sample D. Note that the concentration of boron contained in the boron-doped amorphous diamond film is 3 × 10 ¹⁹ cm ⁻³ .

According to this configuration, in addition to the functions and effects shown in the first embodiment, a positive electrode made of a boron-doped amorphous diamond film having a lower electric resistance than the undoped amorphous diamond film is formed on the p-type cladding layer 5. Since the gate electrode 7 is formed, a current can be made to flow uniformly over the entire surface of the positive electrode 7 as compared with the nitride-based compound semiconductor device according to the first embodiment, and the luminous efficiency can be improved.

(Embodiment 3) Positive electrode 7 according to Embodiment 3
First, on top of the boron-doped amorphous diamond film used in Example 2, indium tin oxide (hereinafter I
(Referred to as TO). The boron-doped amorphous diamond film is formed by the same method as in the second embodiment, and the ITO film is formed by sputtering in an oxygen atmosphere. Hereinafter, the LED according to the third embodiment is referred to as a sample E. The thickness of the ITO film is 1
00 nm.

According to this configuration, in addition to the functions and effects shown in the second embodiment, a boron-doped amorphous diamond film and an IT having an electric resistance smaller than that of the boron-doped amorphous diamond film are formed on the p-type cladding layer 5.
Since the positive electrode 7 made of an O film was formed,
As compared with the semiconductor device according to the above, a current can be made to flow uniformly over the entire surface of the positive electrode 7, and the luminous efficiency can be improved.

(Light Emission Experiment) Next, in order to confirm the effect of the LED according to the second embodiment of the present invention, the following light emission test was performed. For comparison, a conventional LED in which a nickel film and a gold film are sequentially formed on the positive electrode 7 (hereinafter referred to as sample F)
) Was also subjected to a luminescence test. The ratio of the thickness of the nickel film to the thickness of the gold film is as follows: nickel film: gold film = 1:
It is one.

The light emission test was performed by examining the light emission intensity of the LED as viewed from the positive electrode 7 when a certain forward value of the forward current was applied to the LED.

In the second embodiment, the emission intensities of Sample C, Sample D, Sample E and Sample F when the thickness and area of the positive electrode 7 were changed were examined. That is, for Sample C, the thickness of the undoped amorphous diamond film, for Samples D and E, the thickness of the boron-doped amorphous diamond film, and for Sample F, the nickel film thickness and the gold film thickness. Was changed such that the ratio of the film thickness was 1: 1 nickel film: gold film. Hereinafter, the film thickness of the undoped amorphous diamond film, the film thickness of the boron-doped amorphous diamond film, the sum of the film thickness of the boron-doped amorphous diamond film and the film thickness of the ITO film, and the film thickness of the nickel film and the gold film The sum of the thickness and the thickness is collectively referred to as an electrode film thickness.

FIG. 3 shows the case where the area of the positive electrode 7 is 0.5 mm ² , and FIG. 4 shows the case where the area of the positive electrode 7 is 100 mm ² . Shows sex. C in the figure is samples C and D
Indicates data curves of samples D and E, and samples E and F indicate data curves of sample F, respectively.

The following can be seen from FIGS.

First, in any of the samples, in the region where the electrode thickness was small, the emission intensity decreased as the electrode thickness became thin. This is considered to be because the electrode resistance in the lateral direction increases due to the decrease in the electrode film thickness. In each sample, the luminous intensity decreased as the electrode thickness increased in the region where the electrode thickness was large. It is considered that this is because the light transmittance of the positive electrode decreases as the electrode thickness increases.

On the other hand, when the area of the positive electrode 7 was 0.5 mm ² and the electrode film thickness was 12 nm or more, the emission intensity of Sample C became larger than that of Sample F. When the area of the positive electrode 7 is 100 mm ² and the thickness of the electrode is 8 nm or more, the emission intensity of Sample C is reduced to that of Sample F.
Than the emission intensity of This is considered to be because the electrode made of the undoped amorphous diamond film is superior to the electrode made of the nickel film and the gold film in transparency with respect to light emitted from the LED.

The light emission intensity of sample D was higher than that of sample C in all the film thickness regions. This is presumably because the resistivity of the boron-doped amorphous diamond film is lower than the resistivity of the undoped amorphous diamond film.

Further, the luminous intensity of sample E is maximum in all regions of the film thickness. Particularly, when the area of the positive electrode 7 is 100 mm ² , the luminous intensity of sample E is other than that in the region of 20 nm or less in electrode thickness. It was significantly better than the sample. This is presumably because the resistance of the positive electrode 7 was further reduced by forming the ITO film on the boron-doped amorphous diamond film, and the current flowed more uniformly over the entire surface of the positive electrode 7.

In the above-described second embodiment, the positive electrode 7 has been described with respect to amorphous diamond, but single crystal diamond, polycrystalline diamond, or the like may be used instead of amorphous diamond. Although titanium and gold are used for the negative electrode 6, a conductor made of carbon such as graphite, single crystal diamond, polycrystalline diamond, amorphous diamond or the like may be used similarly to the positive electrode 7. However, in order to improve conductivity, an impurity of a Group 5 element is added.

In the second embodiment, the I
In addition to the TO film, a conductive oxide such as iridium oxide,
Alternatively, a similar effect can be obtained by forming a film made of a conductive nitride such as titanium nitride.

(Embodiment 3) A nitride-based compound semiconductor device according to a third embodiment of the present invention is formed on a main surface of a Si-doped n-type GaN substrate 8 as shown in FIG. A GaN layer 11 having a thickness of 2 μm, to which a concentration of Mg which is a Group 2 element is added and having a thickness of 2 × 10 ¹⁹ cm ⁻³ , and a GaN contact layer 12 having a thickness of 50 nm doped with Mg on the GaN layer 11 Is selectively formed, and the electrode 13 is formed on the GaN contact layer 12 (hereinafter, this semiconductor device is referred to as a sample G). The manufacturing method for obtaining this structure is to form the GaN layer 11, the GaN contact layer 12, and the film to be an electrode on the GaN substrate 8 sequentially, and then selectively remove the film to be the electrode to form the electrode 13. Then, the GaN contact layer 12 is etched using the electrode 13 as a mask, and the GaN contact layer 12 is arranged at a predetermined interval. The electrode 13 is composed of an undoped amorphous diamond film having a thickness of 10 nm from the side in contact with the GaN contact layer 12 and a gold film having a thickness of 0.5 μm.

For comparison, a semiconductor device according to a conventional technique (hereinafter, this semiconductor device is referred to as a sample H) using a nickel film having a thickness of 50 nm instead of using an undoped amorphous diamond film having a thickness of 10 nm for the electrode 13 is shown. Produced.

The Mg concentration of the GaN contact layer 12 is set to 1 ×
FIG. 6 shows how the contact resistivity between the GaN contact layer 12 and the electrode 13 changes when the contact resistance is changed from 10 ¹⁸ cm ⁻³ to 2 × 10 ²¹ cm ⁻³ . Contact resistivity is based on the transmission line mode (Transmission Line Mode).
l: TLM) method. In FIG. 6, G indicates the data curve of sample G, and H indicates the data curve of sample H.

FIG. 6 shows that when the Mg concentration is in the range of 1 × 10 ¹⁸ cm ⁻³ to 2 × 10 ²¹ cm ⁻³ , the contact resistivity of Sample G is smaller than the contact resistivity of Sample H. . This is because, when an undoped amorphous diamond film is used for the electrode 13, the work function of carbon is larger than that of nickel, the conduction carriers in diamond are mainly holes, and the GaN contact layer 12 and the electrode 1
This is considered to be because the discontinuity of the valence band potential at the interface with No. 3 is reduced as compared with the case where a nickel film is used.

In the third embodiment, instead of using an amorphous diamond film, a film made of a conductor containing carbon such as graphite, single crystal or polycrystalline diamond may be used. Alternatively, a film in which a conductor including Group 3 elements such as boron is doped may be used.

(Embodiment 4) A nitride-based compound semiconductor device according to a fourth embodiment of the present invention is different from the semiconductor device according to the second embodiment in that the p-type cladding layer 5 shown in FIG. The positive electrode 7 is a film in which an undoped amorphous diamond film and a metal film are sequentially formed.

With this configuration, since the metal film is formed on the undoped amorphous diamond film,
The positive electrode 7 can be easily wire-bonded with gold or the like or fixed with gold-tin solder or the like.

A specific example of the metal film formed on the undoped amorphous diamond film will be described in the following examples.

(Embodiment 4) Al, Ga, I
At least one element of Group 3 elements such as n is used.

According to this configuration, the group III element diffuses into the undoped amorphous diamond film and acts as an impurity, so that the contact resistance between the undoped amorphous diamond film and the metal film can be reduced.

(Embodiment 5) Ti is used as a metal film.

With this configuration, since Ti having good adhesion to diamond is used, peeling of the metal film can be suppressed.

(Embodiment 6) Cr, Ni, C as metal film
At least one metal of u, Mo, Pd, W, Au and Pt is used.

With this configuration, Cr having a large work function,
Since Ni, Cu, Mo, Pd, W, Au or Pt is used, the contact resistance between the undoped amorphous diamond film and the metal film can be reduced.

In the fourth embodiment, in addition to the undoped amorphous diamond film, an amorphous diamond film to which a Group 3 element, for example, boron is added, a single crystal diamond, a polycrystalline diamond, or the like can be used. Good effect can be obtained.

In the fourth embodiment, a film made of a conductive oxide such as an ITO film or a conductive nitride such as a titanium nitride is provided between the undoped amorphous diamond film and the metal film. Even better effects can be obtained by forming.

Although the first, second and fourth embodiments have been described with reference to the case of the positive electrode, the same applies to graphite, amorphous diamond, single crystal diamond or polycrystalline diamond for the negative electrode. May be used.

Although the first to fourth embodiments have been described with respect to the case of a GaN film formed on a substrate, the same applies to graphite, amorphous diamond, and single crystal diamond for a GaN substrate. Alternatively, an electrode including a film made of polycrystalline diamond may be used.

Furthermore, although the first, second and fourth embodiments have been described with reference to the case of LEDs, similar effects can be obtained with other semiconductor devices such as lasers.

According to the first to fourth embodiments, Al _x Ga _{1 -xy} In _y N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) having conductivity instead of GaN is used as a semiconductor layer or a substrate. ,
0 ≦ x + y ≦ 1) may be used.

[0090]

As described above, according to the present invention, it is possible to reduce the possibility of destruction such as a short circuit as compared with a conventional semiconductor device.

Further, according to the present invention, the resistivity of the electrode can be reduced as compared with the conventional semiconductor device.

Further, according to the present invention, the luminous efficiency of a light emitting element such as an LED can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a semiconductor device according to a first embodiment of the present invention;

FIG. 2 is a sectional view of a semiconductor device according to the second embodiment and the fourth embodiment;

FIG. 3 is a diagram showing the electrode film thickness dependence of the light emission intensity of an LED when the area of the positive electrode 7 is 0.5 mm ² in the ^second embodiment.

FIG. 4 shows that the area of the positive electrode 7 is 1 in the second embodiment.
The figure which shows the electrode film thickness dependence of the light emission intensity of LED when it is set to 00 mm ²

FIG. 5 is a sectional view of a semiconductor device according to a third embodiment of the present invention;

FIG. 6 is a diagram showing a relation of contact resistivity between a GaN contact layer 12 and an electrode 13 in a third embodiment.

[Explanation of symbols]

 Reference Signs List 1 sapphire substrate 2 buffer layer 3 n-type cladding layer 4 light emitting layer 5 p-type cladding layer 6 negative electrode 7 positive electrode 8 n-type GaN substrate 11 GaN layer 12 GaN contact layer 13 electrode

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Osamu Imado 1-1, Yukicho, Takatsuki-shi, Osaka, Japan Matsushita Electronics Co., Ltd. (72) Inventor Shinji Nakamura 1-1-1, Yukicho, Takatsuki-shi, Osaka, Matsushita Electronics (72) Inventor Kenji Orita 1-1, Komachi, Takatsuki-shi, Osaka Matsushita Electronics Co., Ltd. F-term (reference) 5F041 AA03 AA23 AA43 CA34 CA40 CA46 CA49 CA57 CA65 CA74 CA82 CA83 CA88 CA92 DA03 DA07 5F073 CA07 CA17 CB05 CB07 CB19 CB22 DA05 EA29 FA27

Claims (17)

[Claims] An Al _x Ga _{1 -xy} In _y N having conductivity
(0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1), and an electrode formed on the semiconductor layer, wherein the electrode includes a film made of carbon. A semiconductor device characterized by the above-mentioned. 2. The semiconductor device according to claim 1, wherein said film made of carbon is a film made of graphite. 3. The semiconductor device according to claim 1, wherein the film made of carbon is a film made of diamond crystals. 4. The film according to claim 1, wherein the film made of carbon is a film made of amorphous diamond.
13. The semiconductor device according to claim 1. 5. The film according to claim 1, wherein the film made of carbon is a film to which a Group 3 element or a Group 5 element is added.
13. The semiconductor device according to claim 1. 6. The semiconductor device according to claim 5, wherein said Group 3 element is boron. 7. The semiconductor device according to claim 5, wherein said Group 5 element is phosphorus. 8. The semiconductor device according to claim 1, wherein the electrode is formed by forming a film made of a conductive oxide on a film made of carbon from the semiconductor layer side. 9. The semiconductor device according to claim 1, wherein said conductive oxide is indium tin oxide. 10. The semiconductor device according to claim 1, wherein the electrode is formed by forming a film made of a conductive nitride on a film made of carbon from the semiconductor layer side. 11. The semiconductor device according to claim 1, wherein the electrode has a metal film formed on a film made of carbon from the semiconductor layer side. 12. The metal film is made of Al, Ga or In.
12. The semiconductor device according to claim 11, comprising at least one kind of metal among the following. 13. The semiconductor device according to claim 11, wherein said metal film contains Ti. 14. The metal film is made of Cr, Ni, Cu, M
12. The semiconductor device according to claim 11, comprising at least one metal selected from the group consisting of o, Pd, W, Au, and Pt. 15. The semiconductor device according to claim 1, wherein the semiconductor layer is a layer to which a Group 2 element is added. 16. The semiconductor according to claim 15, wherein said Group 2 element is Mg, and the concentration of Mg is 2 × 10 ¹⁸ cm ⁻³ or more and 1 × 10 ²¹ cm ⁻³ or less. apparatus. 17. Al _x Ga _{1 -xy} I having conductivity
a substrate made of n _y N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1); and an electrode formed on the substrate, wherein the electrode includes a film made of carbon. A semiconductor device characterized by the above-mentioned.