JP2006032863A - Electrode for n-type nitride semiconductor layer and its manufacturing method and light emitting element containing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an n-side electrode which is reduced in surface roughness at the time of heat treatment performed for reducing a contact resistance without any impairment in ohmic contact with an n-type GaN semiconductor layer, and also to provide its manufacturing method and a light emitting element containing the same. <P>SOLUTION: An electrode P1 for an n-type nitride semiconductor layer is an electrode for ohmic contact formed on the surface of the n-type GaN semiconductor layer 1. At least the region of the electrode in contact with the n-type GaN semiconductor layer 1 consists of an Al-Nd alloy formed of substantially two elements including aluminum and neodymium. A preferred manufacturing method of the electrode P1 comprises a process of forming a thin film consisting of an aluminum alloy which is substantially formed of two elements of aluminum and neodymium on the surface of the n-type GaN semiconductor layer 1, and is a solid solution of aluminum and neodymium, and a process of heat-treating the thin film to accelerate deposition. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrode for an n-type nitride semiconductor layer formed so as to obtain ohmic contact on an n-type nitride semiconductor layer of a nitride semiconductor element such as a light-emitting element, a light-receiving element, and an electronic device, The present invention relates to a manufacturing method and a light emitting device made of a nitride semiconductor having the manufacturing method.

A nitride semiconductor is a compound composed of a group III nitride determined by the formula Al _α In _β Ga _γ N (0 ≦ α ≦ 1, 0 ≦ β ≦ 1, 0 ≦ γ ≦ 1, 0 ≦ α + β + γ ≦ 1). Examples of semiconductors include GaN (gallium nitride) AlN (aluminum nitride), InN (indium nitride), and mixed compositions such as InGaN, AlGaN, and AlInGaN. In recent years, a nitride semiconductor light emitting device having a structure in which an n-type GaN-based semiconductor layer, a light-emitting layer, and a p-type GaN-based semiconductor layer are stacked in this order has been put into practical use, and the material composition of the nitride semiconductor used for the light-emitting layer has been changed. By selecting, it is possible to generate short wavelength light ranging from blue to ultraviolet.
Hereinafter, the “nitride semiconductor” is also referred to as “GaN-based semiconductor”, and for example, if “nitride semiconductor light-emitting device” is also referred to as “GaN-based semiconductor light-emitting device”, the prior art and the present invention are described.

  FIG. 2 is a diagram showing an example of a general element structure of a GaN-based LED which is one of GaN-based semiconductor elements. A GaN-based low-temperature growth buffer layer B2 is formed on a crystal substrate B1 such as a sapphire substrate. Thus, a laminated body composed of GaN-based semiconductor layers is formed. The laminate has a pn junction structure composed of an n-type GaN-based semiconductor layer and a p-type GaN-based semiconductor layer, and a light emitting layer is formed at the junction. Specifically, a laminated structure such as an n-type cladding layer 1 (which also serves as an n-type contact layer in this example) and a light-emitting layer (multiple quantum wells) may be sequentially formed from the lower side (crystal substrate side). 2) A p-type cladding layer 3 (which also serves as a p-type contact layer in this example) 3 is laminated by vapor phase growth. P1 and P2 are an n-side electrode and a p-side electrode, respectively.

  The n-type nitride semiconductor is a nitride semiconductor in which the carriers that carry charge are mainly electrons among the above-described nitride semiconductors. Generally, the nitride semiconductor includes Si (silicon), Ge (germanium), It is obtained by doping with an n-type dopant such as C (carbon), Se (selenium), Te (tellurium) or the like. Hereinafter, the n-type nitride semiconductor is also referred to as “n-type GaN-based semiconductor”.

In a GaN-based semiconductor element, an electrode that makes ohmic contact with the GaN-based semiconductor layer is required. As an electrode that is in ohmic contact with an n-type GaN-based semiconductor layer (also referred to as “n-side electrode”), an electrode made of Al (aluminum) alone is known (Patent Document 1).
However, an Al electrode made of Al alone has a rough surface during heat treatment at 350 ° C. to 600 ° C. which is usually performed in order to increase the adhesion between the electrode material and the semiconductor and reduce the contact resistance (specifically, , The formation of protrusions called hillocks and holes called voids or pits). When the surface of the electrode is roughened, there is a problem that the bonding property when an Au (gold) wire for energization is bonded to the electrode is lowered. Similarly, when the device is flip-chip bonded, there is a problem in that the bonding property with a brazing material (solder or the like) or conductive adhesive used for bonding with the lead electrode is lowered.
In addition, Al is easy to form an oxide film on the surface, so that it is chemically stable. On the other hand, the wettability by the molten metal is lowered, so that it is too good in terms of bondability with the Au wire and brazing material. I can't say that.

  In order to solve the above problem of the Al electrode, the region in contact with the n-type nitride semiconductor layer is an Al layer, the surface side is an Au layer that is difficult to oxidize, and further, the reaction between the Al layer and the Au layer is prevented in the middle An n-side electrode having a multilayer structure in which an intermediate layer is provided has been proposed (Patent Document 2). In addition, it is known that the above-described problems of the Al single film can be improved by adding Ti (titanium) to Al to form an Al—Ti alloy (Patent Document 3).

However, the main causes of the remarkable surface roughness during the heat treatment in the Al electrode formed on the nitride semiconductor are the thermal expansion coefficient of Al (about 23 × 10 ⁻⁶ K ⁻¹ ) and the thermal expansion coefficient of the GaN-based semiconductor ( large difference between about 6 × 10 -6 ^{K -1)} is, since the Al layer is to surrender deformed strong stress is generated by temperature changes during the heat treatment, the disclosed in Patent Document 2 electrode multilayer It is difficult to solve this problem only by structuring. That is, the method of Patent Document 2 considers that the cause of surface roughness is that the melting point of Al is low, and devised the structure of the protective layer provided on the Al layer in order to reduce the thermal effect on the Al layer. However, it does not change the characteristics of the Al layer itself. For this reason, the influence of deformation generated in the Al layer reaches the upper intermediate layer and Au layer, resulting in surface roughness. In a severe case, a through hole is formed in the intermediate layer, and the effect of suppressing the reaction between the Al layer and the Au layer cannot be obtained.
Al alloying, on the other hand, is an excellent method for improving the characteristics of Al itself, but improves the Al deformation resistance during heat treatment without extremely deteriorating ohmic properties with the n-type GaN-based semiconductor. As an additive element to be obtained, no appropriate element has been found in addition to Ti.
Japanese Patent Laid-Open No. 55-9442 Japanese Patent Laid-Open No. 10-247746 JP 7-45867 A

  An object of the present invention is to provide an n-side electrode in which surface roughness during heat treatment for reducing contact resistance is suppressed without impairing ohmic properties with an n-type GaN-based semiconductor layer, a manufacturing method thereof, and a light-emitting element having the same This improves the bonding efficiency between the Au wire or brazing material and the n-side electrode when performing wire bonding or flip chip bonding, and improves the manufacturing efficiency and reliability of GaN-based semiconductor elements. It is something that is going to be raised.

The present invention has the following features.
(1) An electrode for ohmic contact formed on the surface of an n-type nitride semiconductor layer, wherein at least a region in contact with the n-type nitride semiconductor layer is substantially made of aluminum and neodymium. An electrode for an n-type nitride semiconductor layer formed of an Al—Nd alloy made of an element.
(2) The electrode according to (1), wherein the content of neodymium in the Al—Nd alloy is 0.7 atomic% to 10 atomic%.
(3) The electrode according to (2) above, wherein the Al—Nd alloy contains an intermetallic compound composed of aluminum and neodymium.
(4) The electrode according to any one of (1) to (3), further including a bonding metal layer formed on a region formed of the Al—Nd alloy.
(5) The electrode according to (4), further including a barrier layer formed between the region formed of the Al—Nd alloy and the bonding metal layer.
(6) The method further includes an alternate laminate formed by alternately laminating two or more layers made of gold and platinum, each of which is formed on the region formed of the Al—Nd alloy. The electrode according to any one of 1) to (3).
(7) forming on the surface of the n-type nitride semiconductor layer a thin film made of an aluminum alloy substantially composed of two elements of aluminum and neodymium and in which neodymium is dissolved in aluminum; and heat-treating the thin film. And a method for producing an electrode for an n-type nitride semiconductor layer, comprising a step of strengthening the precipitation.
(8) The production method according to (7), wherein the content of neodymium in the aluminum alloy is 0.7 atomic% to 10 atomic%.
(9) The manufacturing method according to the above (7) or (8), wherein the thin film made of the aluminum alloy is formed by sputtering.
(10) The manufacturing method according to any one of (7) to (9), wherein the temperature of the heat treatment is 150 ° C to 600 ° C.
(11) The manufacturing method according to (10), wherein the temperature of the heat treatment is 350 ° C. to 600 ° C.
(12) A nitride semiconductor light emitting device having the electrode according to any one of (1) to (6).

The electrode for an n-type GaN-based semiconductor layer of the present invention has the following effects.
(1) Good ohmic contact can be obtained with the n-type GaN-based semiconductor layer.
(2) Roughness of the surface when heat treatment for reducing contact resistance is performed is greatly suppressed, and as a result, the bondability with Au wire, brazing material, and conductive adhesive is good.
The fact that the effects of (1) and (2) can be obtained at the same time has been confirmed for the first time by the experiments and researches of the present inventors, and is an unexpected result from the prior art. The detailed reason why such an effect is obtained is not clear, but for (2), solid solution strengthening of Al by addition of Nd and precipitation strengthening by precipitation of excessively added Nd as an intermetallic compound or the like. As a result of this, it is considered that the deformation resistance is improved as compared with the case of using Al alone. On the other hand, for (1), in the process of precipitation strengthening, a region with a low solid solution concentration of Nd is generated, and the electrical properties of the entire Al—Nd alloy layer strongly reflect the properties of the region, The present inventors presume that it is likely to approach Al alone.
The electrode for the n-type GaN-based semiconductor layer of the present invention is optically similar to Al alone and has high reflectivity for short-wavelength light from blue to ultraviolet generated by the GaN-based semiconductor light-emitting element. Therefore, it can be particularly suitably used as an electrode for a GaN-based semiconductor light emitting device.

Hereinafter, the present invention will be described using a GaN-based LED, which is a GaN-based semiconductor element, as an example.
As described above, the element structure of the GaN-based LED has an element structure in which a GaN-based semiconductor layer is sequentially grown on the crystal substrate B1 and the buffer layer B2 to form a stacked body, as shown in FIG. The stacked body includes an n-type GaN-based semiconductor layer 1, a light emitting layer 2, and a p-type GaN-based semiconductor layer 3 in order from the lower layer side. The n-type GaN-based semiconductor layer 1 may include an n-type contact layer and an n-type cladding layer independently. In the example of FIG. 1, only one layer is used as both layers. The light emitting layer 3 is a layer for causing light emission by recombination of carriers, and may be a laminated structure as well as a single layer.

  FIG. 1 is an enlarged view of an electrode for an n-type GaN-based semiconductor layer according to the present invention. Although FIG. 1 shows an electrode having a three-layer structure, the electrode of the present invention is not limited to a three-layer structure. The electrode P1 for the n-type GaN-based semiconductor layer according to the present invention is characterized in that at least a region P11 in contact with the n-type GaN-based semiconductor layer 1 of the electrode is substantially Al— consisting of two elements of Al and Nd. It is a point formed with an Nd alloy. Here, “substantially” means an alloy containing only two elements of Al and Nd, excluding inevitable impurities derived from the manufacturing process and the like.

In the electrode P1 for the n-type GaN-based semiconductor layer, a region P11 in contact with the n-type GaN-based semiconductor layer is a region including a contact surface with the n-type GaN-based semiconductor layer 1.
In the electrode P1 for the n-type GaN-based semiconductor layer of the present invention, the thickness of the region P11 formed from the Al—Nd alloy can be 1 nm to 2000 nm. If the thickness is less than 10 nm, the Al—Nd alloy becomes a thin film that adheres to the surface of the n-type GaN-based semiconductor layer in an island shape. Therefore, due to the difference in thermal expansion coefficient between the Al—Nd alloy and the GaN-based semiconductor during heat treatment. It is preferable in that the generated stress is relaxed and hillocks are hardly formed. However, when the thickness is smaller than 1 nm, the contact area between the Al—Nd alloy and the GaN-based semiconductor surface becomes small, so that the ohmic property is lowered. Or the contact resistance tends to increase.

  In the case where the n-side electrode P1 has a multilayer structure as illustrated in FIG. 1, the thickness of the region P11 made of an Al—Nd alloy is such that an ohmic property with the n-type GaN-based semiconductor layer is achieved. And preferably 1 nm to 500 nm. However, depending on the type of metal constituting the upper layer, it diffuses to the vicinity of the interface between the Al—Nd alloy layer and the n-type GaN-based semiconductor layer during the heat treatment, and the Al—Nd alloy and the n-type GaN-based semiconductor layer Therefore, the thickness of the region P11 is more preferably 10 nm or more, and further preferably 30 nm or more.

  The electrode P1 for the n-type GaN-based semiconductor layer of the present invention may be a single layer of an Al—Nd alloy. In this case, the thickness of the electrode P1 is the same as that of a lead electrode using wire bonding or brazing material. The thickness is preferably 50 nm or more, more preferably 100 nm or more, and still more preferably 200 nm or more so that it can withstand the impact received in the bonding step. There is no particular upper limit to the thickness of the n-side electrode P1 made of a single layer of Al—Nd alloy, but the effect does not change even if it is thicker than 1000 nm. From the viewpoint of reducing material consumption, it should be 1000 nm or less. Is preferred.

In the electrode for an n-type GaN-based semiconductor layer of the present invention, the region P11 made of an Al—Nd alloy forms a thin film made of an Al alloy in which an amount of Nd exceeding the solid solubility limit in an equilibrium state is dissolved in Al. Thereafter, it is obtained by heat treatment. In the course of this heat treatment, some Nd precipitates as Al ₄ Nd intermetallic compounds, etc., so that the presence mode and concentration of Nd in the alloy may become microscopically uneven. The content is the same as the content at the time of film formation.
The preferred Nd content of the Al—Nd alloy needs to be higher than 0.05 atomic%, preferably 0.7 atomic% to 10 atomic%, particularly preferably about 2 atomic% (1.8 to 2). .2 atomic%). When the Nd content is 0.05 atomic% or less, precipitation strengthening due to heat treatment does not occur sufficiently. If the Nd content exceeds 10 atomic%, the ohmic property with the n-type GaN-based semiconductor tends to decrease.

If the temperature of the heat treatment of the Al—Nd alloy is higher than 150 ° C., precipitation of the Al ₄ Nd intermetallic compound occurs and precipitation strengthening occurs. Preferably, it is 400 ° C. or higher. The heat treatment temperature must be a temperature that does not exceed the melting point of Al, and is preferably 600 ° C. or lower.
Although the preferable heat treatment time depends on the heat treatment temperature, for example, the heat treatment time may be maintained at 300 ° C. or higher for 1 minute or longer, and the temperature does not change during that time.
As the heat treatment method itself, a known method may be used. For example, a resistance heating type heat treatment furnace or a lamp heating furnace (also called a rapid thermal annealing apparatus: also called an RTA apparatus) may be used.
The heat treatment step may be performed exclusively as a heat treatment for precipitation strengthening of the Al—Nd alloy, but other processes involving heating (for example, the contact resistance between the n-side electrode and the n-type nitride semiconductor) You may utilize the heating in the heat processing process for reducing, and the formation process of an insulating protective film.
The atmosphere during the heat treatment is preferably an inert gas atmosphere such as nitrogen or a rare gas in order to suppress surface oxidation, particularly when the n-side electrode is a single layer made of an Al—Nd alloy. . When a bonding metal layer to be described later is formed on the surface, the atmosphere is not particularly limited because the surface is difficult to be oxidized.

  The method of forming on the surface of the n-type GaN-based semiconductor layer 1 a thin film made of an Al alloy in which an amount of Nd exceeding the solid solubility limit in the equilibrium state is dissolved in Al is a method capable of forming a thin film having a non-equilibrium composition. There is no particular limitation as long as it is, but preferably sputtering is used, and the target is prepared by a method such as a melt casting method, a spray forming method, a powder sintering method, or the like. Examples include a method using an alloy sputtering target dispersed in the form of a compound, or a method using a split sputtering target in which an Al chip and an Nd chip are combined.

As illustrated in FIG. 1, an electrode P1 for an n-type GaN-based semiconductor layer according to the present invention includes a barrier layer P12 and a bonding metal layer P13 sequentially formed on a region P11 formed of the Al—Nd alloy. It is good also as a multilayer structure which has further.
The barrier layer P12 prevents an alloying reaction between the region P11 formed of the Al—Nd alloy and the bonding metal layer P13 during the heat treatment for reducing the contact resistance between the n-side electrode and the n-type GaN-based semiconductor. The bonding metal layer P13 is for improving the wettability between the molten brazing material such as Au or Au—Sn alloy solder and the n-side electrode surface during wire bonding or flip chip bonding. Layer.

For the purpose, the material of the barrier layer P12 is a metal material having a melting point higher than that of the material constituting the Al—Nd alloy and the bonding metal layer P13. For example, if Au or an Au alloy is used for the bonding metal layer P13, Co (cobalt), Ti (titanium), W (tungsten), Mo (molybdenum), Pt (as a metal material having a higher melting point). Examples include platinum), Ir (iridium), Pd (palladium), Rh (rhodium), Ni (nickel), and alloys thereof.
The thickness of the barrier layer P12 is preferably 10 nm or more, more preferably 30 nm or more. The upper limit of the thickness of the barrier layer P12 is not particularly defined, but since the effect does not change even when the thickness is greater than 100 nm, 100 nm is generally mentioned.

For the purpose, the material of the bonding metal layer P13 is at least a material that is less likely to be oxidized than the material constituting the Al—Nd alloy layer and the barrier layer provided thereunder. Most preferable is Au (including an alloy containing Au as a main component).
The thickness of the bonding metal layer P13 is preferably 50 nm to 2000 nm.

In the aspect in which the electrode P1 for the n-type GaN-based semiconductor layer has a multilayer structure, various functional layers are further provided between the region P11 formed of the Al—Nd alloy, the barrier layer P12, and the bonding metal layer P13. Alternatively, the barrier layer P12 and the bonding metal layer P13 may each include a layer with a changed composition, and each layer may have a multilayer structure or a composition-graded layer.
As a preferred embodiment, for example, an alternating layer in which two or more Pt layers and Au layers are formed on a region formed of an Al—Nd alloy, the lowermost layer is a Pt layer, and the uppermost layer is an Au layer. Forming a laminated body is mentioned. Here, the Pt layer is a layer made of platinum (or an alloy containing platinum as a main component), and the Au layer is a layer made of gold (or an alloy containing gold as a main component). Further, the lowermost layer of the alternate laminate may be a layer made of one or more metals selected from Co, Ti, W, Mo, Ir, Pd, Rh, and Ni, instead of the Pt layer.

  In the embodiment in which the electrode P1 for the n-type GaN-based semiconductor layer has a multilayer structure, when only the region P11 made of an Al—Nd alloy is formed, the contact resistance between the electrode and the n-type GaN-based semiconductor is reduced. The heat treatment may be performed. In this case, if there is no subsequent step of exposing the electrode layer to high temperature, the barrier metal layer P12 can be omitted and the bonding metal layer P13 can be provided directly on the region P11.

  The nitride semiconductor light emitting device according to the present invention is a device having the electrode according to the present invention described above in an n-type layer. The prior art may be referred to for the laminated structure of the element itself.

Examples 1-3
Three n-type sapphire substrates with a diameter of 2 inches were prepared, and Si-doped n-type via a low-temperature buffer layer made of GaN grown at 400 ° C. on each surface by using an organic metal compound vapor phase growth method. The GaN-based semiconductor layer was grown at a growth temperature of 1000 ° C. to a thickness of 3 μm.
A photoresist film having a predetermined electrode pattern (described later) as an opening is formed on the surface of the n-type GaN-based semiconductor layer using an ordinary photolithography technique, and then Al—Nd having a thickness of 400 nm is formed by sputtering. An alloy thin film was formed. The apparatus used for sputtering is a DC magnetron sputtering apparatus. As a target, a predetermined amount of a 5 mm square Nd chip (purity of 99.99%) is placed on a pure Al target (purity of 99.99% or more). By using the installed composite target and changing the installation amount of the Nd chip, the Nd content of the Al—Nd alloy thin film of each sample is 1 atomic% (Example 1), 2 atomic% (Example 2), 4 Atomic% (Example 3). The Nd content was confirmed by inductively coupled plasma (ICP) emission spectroscopic analysis.
After the formation of the Al—Nd alloy thin film, the photoresist film is lifted off so that the shape of each electrode when viewed from the wafer surface is a circle having a diameter of 100 μm, and the circular electrodes are 50 × 50 with a center-to-center pitch of 350 μm. An electrode pattern arranged in a square matrix was obtained.
Thereafter, the sample was placed in a rapid thermal annealing apparatus (RTA apparatus), and was subjected to heat treatment (annealing) at 400 ° C. for 3 minutes in a nitrogen atmosphere.
Next, IV (current-voltage) characteristics were measured between all adjacent pairs of electrodes arranged in the above pattern. The range of the current value during measurement was 0 to 20 mA. As a result, in any of the samples in which the Nd content of the electrode made of the Al—Nd alloy was 1 atomic% (Example 1), 2 atomic% (Example 2), and 4 atomic% (Example 3), Since the IV characteristics between the electrodes became linear, it was found that the electrodes were ohmic.
In any of the samples of Examples 1 to 3, the electrode surface after the heat treatment had a metallic luster, and when observed with a differential interference microscope, hillocks and voids were not observed at all and were smooth. It was.

Examples 4-6
Three n-type sapphire substrates with a diameter of 2 inches were prepared, and Si-doped n-type via a low-temperature buffer layer made of GaN grown at 400 ° C. on each surface by using an organic metal compound vapor phase growth method. A Ga _0.9 Al _0.1 N layer was grown at a growth temperature of 1100 ° C. to a thickness of 3 μm.
On the surface of the n-type Ga _0.9 Al _0.1 N layer, an electrode made of an Al—Nd alloy having a thickness of 300 nm was formed in the same pattern as in Example 1 by the same method as in Example 1. The Nd content of the Al—Nd alloy electrode of each sample was 1 atomic% (Example 4), 2 atomic% (Example 5), and 4 atomic% (Example 6), respectively.
In the same manner as in Example 1, the IV characteristics were measured after the heat treatment, and the IV characteristics between the electrodes in any of the samples of Example 4, Example 5, and Example 6. Was linear and the electrode was found to be ohmic.
In any of the samples of Examples 4 to 6, the electrode surface after the heat treatment had a metallic luster, and when observed with a differential interference microscope, hillocks and voids were not observed at all and were smooth. It was.

Example 7
In Example 1, instead of using an Al—Nd alloy thin film as the electrode, a 100 nm thick Al—Nd alloy (Nd content: 2 atom%) thin film, a 50 nm thick Pd thin film, and a 400 nm thick Au thin film were used. A sample composed of multilayer films laminated in this order was prepared. The Al—Nd alloy thin film was formed by sputtering in the same manner as in Example 2, and the Pd thin film and Au thin film to be laminated thereon were formed by using an electron beam heating vacuum deposition apparatus. After the uppermost Au thin film was formed, the photoresist film was lifted off to obtain a patterned electrode in the same manner as in Example 1, followed by heat treatment at 450 ° C. for 1 minute.
About the obtained sample, when the IV characteristic was measured like the case of Example 1, the IV characteristic between each electrode became linear and the electrode became ohmic property.
Further, the electrode surface after the heat treatment had a metallic luster, and when observed with a differential interference microscope, hillocks and voids were not observed at all and were smooth.

Comparative Example 1
In Example 1, except that the Nd content of the Al—Nd alloy was set to 0.05%, an electrode was produced by the same method as in Example 1. As a result, the surface of the electrode after the heat treatment lost metallic luster. When observed with a differential interference microscope, many hillocks and voids were observed.

Comparative Example 2
In Example 7, except that the Nd content of the Al—Nd alloy thin film was set to 0.05%, an electrode was produced by the same method as in Example 1. As a result, the electrode surface after the heat treatment lost metallic luster. When observed with a differential interference microscope, many hillocks and voids were observed.

Example 8
A GaN low-temperature growth buffer layer, an n-type GaN cladding layer, an InGaN light-emitting layer, a p-type AlGaN cladding layer, and a p-type GaN contact layer are sequentially grown on a sapphire substrate having a diameter of 2 inches by using an organic metal compound vapor deposition method. Thus, an LED wafer having an emission wavelength of 400 nm was produced. Thereafter, electrode formation and element isolation were performed, and the cross-sectional structure shown in FIG. 2 (where the p-type cladding layer and the p-type contact layer are formed of different layers), the top surface shape was substantially square, and the size was 300 μm × A 300 μm LED element was obtained. For the n-side electrode, the InGaN light-emitting layer, the p-type AlGaN cladding layer, and the p-type GaN contact layer are partially removed from the GaN-based semiconductor layer lamination side of the LED wafer by dry etching, and the exposed n-type GaN cladding layer The same procedure as in Example 7 was performed on the surface. That is, a multilayer film formed by laminating a 100 nm thick Al—Nd alloy (Nd content: 2 atom%) thin film, a 50 nm thick Pd thin film, and a 400 nm thick Au thin film in this order is formed in a predetermined electrode shape. Then, it formed by heat-processing at 450 degreeC for 1 minute. As the p-side electrode, a pad electrode made of Au was formed on a normal transparent ohmic electrode formed by laminating Ni and Au. The obtained LED element had good wire bonding properties, and the output in a bare chip state at an energization current of 20 mA was 5 mW.

It is the figure which expanded the electrode for n type GaN system semiconductor layers of the present invention. It is the figure which showed an example of the general element structure of GaN-type LED.

Explanation of symbols

P1 n-side electrode P2 p-side electrode 1 n-type GaN-based semiconductor layer 2 light-emitting layer 3 p-type GaN-based semiconductor layer

Claims (12)

  An ohmic contact electrode formed on the surface of the n-type nitride semiconductor layer, and at least a region in contact with the n-type nitride semiconductor layer is substantially composed of two elements of aluminum and neodymium. An electrode for an n-type nitride semiconductor layer formed of an Al—Nd alloy.   The electrode according to claim 1, wherein the content of neodymium in the Al—Nd alloy is 0.7 atomic% to 10 atomic%.   The electrode according to claim 2, wherein the Al—Nd alloy includes an intermetallic compound composed of aluminum and neodymium.   The electrode according to claim 1, further comprising a bonding metal layer formed on a region formed of the Al—Nd alloy.   The electrode according to claim 4, further comprising a barrier layer formed between the region formed of the Al-Nd alloy and the bonding metal layer.   4. The apparatus further comprises an alternate laminate formed by alternately laminating two or more layers made of gold and layers made of platinum, which are formed on the region formed of the Al—Nd alloy. The electrode according to any one of the above.   forming a thin film made of an aluminum alloy substantially composed of two elements of aluminum and neodymium and having neodymium dissolved in aluminum on the surface of the n-type nitride semiconductor layer; And a method of manufacturing an electrode for an n-type nitride semiconductor layer.   The manufacturing method of Claim 7 whose content of neodymium in the said aluminum alloy is 0.7 atomic%-10 atomic%.   The manufacturing method according to claim 7 or 8, wherein the thin film made of the aluminum alloy is formed by sputtering.   The temperature of the said heat processing is 150 to 600 degreeC, The manufacturing method as described in any one of Claims 7-9.   The manufacturing method of Claim 10 whose temperature of the said heat processing is 350 to 600 degreeC.   A nitride semiconductor light emitting device comprising the electrode according to claim 1.

Images