JP2015060854A - Nitride semiconductor light-emitting diode and process of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to reduce an energy difference of Schottky barriers with a GaN layer and to efficiently activate carriers in p-GaN.SOLUTION: A nitride semiconductor light-emitting diode 10A includes: a light-emitting layer 14 on a substrate 11; a laminated p-GaN layer 15 on a surface of the light-emitting layer; a laminated MgNi layer 16 on a surface opposite to the p-GaN layer; and, preferably, a palladium layer interposed between the MgNi layer and the p-GaN layer.

Description

  The present invention relates to a nitride semiconductor light-emitting diode and a method for manufacturing the same, and more particularly to a nitride semiconductor light-emitting diode effective for improving performance by promoting activation of a p-GaN layer and a method for manufacturing the same.

In recent years, light emitting diodes (LEDs) have been required to increase brightness and light quantity, and it has been a problem to improve luminous efficiency by reducing contact resistance and the like. First, the configuration of a conventional light emitting diode, particularly the configuration of a non-light emitting portion (electrode) will be described.
FIG. 28 is a cross-sectional view of a conventional nitride semiconductor light-emitting diode as described in Patent Document 1, and is also a schematic diagram for explaining the main part. The nitride semiconductor light emitting diode 10C is configured by sequentially laminating a buffer layer 12, an n-type cladding layer 13, a light emitting layer 14, and a p-type cladding layer 15 on the surface of a Si substrate 11 as a support substrate. Hereinafter, the light emitting diode may be referred to as an LED element.

  Patent Document 2 describes a method of taking a conventional LED structure into a flip chip and taking out light from the back surface of the substrate as a structure that does not reduce the light emitting area. However, this method requires a transparent substrate such as silicon carbide (SiC) or sapphire for the support substrate, but SiC and sapphire are disadvantageous in that they are more expensive than Si.

  By the way, the LED is required to reduce the resistance of p-GaN in order to reduce power consumption and heat generation. Therefore, when nitride-based light-emitting diodes or laser diodes (LD) are formed by metal organic chemical vapor deposition (MOCVD), carrier activation is performed to reduce the resistance of the p-type layer as in Patent Documents 3 and 4. A process is required. This carrier activation process is performed, for example, at 800 to 1000 ° C. as activation annealing.

Non-Patent Document 1 describes that Mg ₂ Ni is a material that stores hydrogen more easily than other alloys. Non-Patent Document 2 describes that palladium Pd is a material that easily permeates hydrogen due to the proton effect.

JP 2010-232649 A JP 2009-049342 A Japanese Patent No. 2540791 JP-A-2-257679

“Current Status and Recent Research and Development of Hydrogen Storage Alloys”, Yotaro Murakami, www.ostec.or.jp/nmc/TOP/34.pdf J. Shuet.al., “AtalyticPalladium-Based Membrane Reactors: A Review,” Canadian J. Chem. Eng., 69, 1036-1060 (1991)

The LED can extract light from the surface by using a transparent electrode such as ITO (indium tin oxide) or ZnO (zinc oxide). However, the p-GaN layer constituting the nitride semiconductor light emitting diode has a very large energy from the vacuum level to the Fermi level of about 7 eV, and ITO (Indium Tin Oxide) has a work function from the vacuum level. However, it is an unstable material that varies with the composition and formation conditions of approximately 4.1 to 4.7 eV. For this reason, the junction between the p-GaN layer and the ITO electrode is a Schottky junction, and efficient power supply to the light emitting layer cannot be performed.
In addition, the p-type electrode 20 shown in FIG. 28 uses a Ni / Au electrode in order to increase ohmic properties, but lacks light transmittance and is not suitable for a light emitting element. Note that the work function of Ni is 5.2 eV and the work function of Au is 5.1 eV, both of which have high values.
Therefore, it is required to reduce the energy difference of the Schottky barrier between the p-GaN layer and aim for ohmic properties. In this regard, it is conceivable that a Ni alloy having a work function higher than that of ITO is interposed between the ITO film (transparent conductive film) and the p-GaN layer.

  By the way, even if activation annealing is performed, the carrier to be activated cannot obtain sufficient carriers with about 10% of the concentration doped in p-type gallium nitride (p-GaN). In order to reduce the resistance, it is conceivable to increase the doping amount of Mg, but the crystallinity of GaN deteriorates as the doping amount increases, so that the reduction in resistance is limited.

  Therefore, the present invention can reduce the energy difference of the Schottky barrier with the GaN layer, and can efficiently activate the carriers in the p-GaN, and the transparent electrode An object is to provide a film forming method.

In order to achieve the above object, a nitride semiconductor light emitting diode of the present invention is a nitride semiconductor light emitting diode comprising a light emitting layer and a p-GaN layer stacked on the surface of the light emitting layer, wherein the p-GaN An Mg ₂ Ni layer laminated on the surface of the layer opposite to the light emitting layer is provided. Here, the light emitting layer opposite surface means a surface opposite to the light emitting layer, and the light emitting layer opposite surface of the p-GaN layer is not bonded to the light emitting layer and the p-GaN layer. Say the face. Moreover, it is preferable to interpose a palladium layer between the Mg ₂ Ni layer and the p-GaN layer.

Using magnesium nickel (Mg ₂ Ni), which is one of the hydrogen storage materials, and palladium (Pd), which is one of the materials that allow hydrogen permeation by the proton effect, the Schottky barrier is reduced and the p-GaN is reduced. Realize resistance. Also, the carriers in p-GaN are activated efficiently. In addition, since the process load can be reduced, the crystallinity of GaN can be maintained as compared with the conventional process, so that the deterioration of the LED can also be prevented. Note that Mg ₂ Ni and Pd can be used as they are as p-GaN electrodes.

Further, if the Mg ₂ Ni / Pd / GaN structure is used, the high work function (p-GaN: about 7 eV, ITO: about 4.2 eV, Pd: about 5.2 eV) possessed by Pd increases the Schottky barrier height. Is reduced, and good contact is achieved. Moreover, since ITO is not brought into direct contact with the p-GaN layer, it is possible to prevent the oxygen of the ITO from oxidizing the p-GaN layer and causing deterioration of the device.

  According to the present invention, the energy difference of the Schottky barrier with the GaN layer can be reduced, and carriers in the p-GaN layer can be activated efficiently.

It is sectional drawing which shows the structure of the nitride semiconductor light-emitting diode which is 1st Embodiment of this invention. It is a band figure for demonstrating a pn junction and an ohmic junction. It is a graph illustrating the relationship between the transmittance and the wavelength of the light Mg ₂ Ni / ITO film. It is a flowchart which shows the manufacturing process of 1st Embodiment. It is sectional drawing which shows the LED structure formed by MOCVD. FIG. 3 is a cross-sectional view of an element in a state where an Mg ₂ Ni film is formed and activated and annealed. Is an element cross-sectional view of a state in which the removal of the Mg 2 _Ni film with hydrofluoric acid. It is an element cross-sectional view of a state in which deposited mg ₂ Ni film · ITO film. It is element sectional drawing for demonstrating a 1st patterning process. It is element sectional drawing for demonstrating a dry etching process. It is element sectional drawing for demonstrating a 2nd patterning process. It is element sectional drawing for demonstrating the process of depositing a p-type electrode. It is element sectional drawing for demonstrating a lift-off process. It is a state diagram of mg ₂ Ni. It is the principle figure of droplet generation | occurrence | production, and a surface photograph. It is a flowchart which shows the manufacturing process of 2nd Embodiment. It is element sectional drawing for demonstrating the 1st patterning process in 2nd Embodiment. FIG. 5 is a device structure diagram in a state where a Pd / Mg ₂ Ni film is deposited. It is element sectional drawing for demonstrating a 2nd patterning process. It is element sectional drawing for demonstrating the dry etching process in 2nd Embodiment. It is element sectional drawing of the state in which the p-type electrode was formed. It is a flowchart which shows the manufacturing process of 3rd Embodiment. It is element sectional drawing for demonstrating the 1st patterning process in 3rd Embodiment. Mg ₂ Ni film, a transparent conductive material (ITO film) is an element cross-sectional view of the deposited state. It is element sectional drawing for demonstrating the 2nd patterning process in 3rd Embodiment. It is element sectional drawing for demonstrating the dry etching process in 3rd Embodiment. It is a flowchart showing a manufacturing process of the nitride semiconductor light emitting diode that does not form a mg 2 _Ni film. It is sectional drawing of the nitride light emitting diode of a conventional structure.

  Hereinafter, an embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described in detail with reference to the drawings. Each figure is only schematically shown so that the present invention can be fully understood. Therefore, the present invention is not limited to the illustrated example. Moreover, in each figure, the same code | symbol is attached | subjected about the common component and the same component, and those overlapping description is abbreviate | omitted.

(First embodiment)
FIG. 1 is a cross-sectional view showing the configuration of the nitride semiconductor light emitting diode according to the first embodiment of the present invention.
In FIG. 1, a nitride semiconductor light emitting diode 10 </ b> A has a buffer layer 12 laminated on the surface of a Si substrate, sapphire substrate, or SiC substrate 11 (hereinafter referred to as “substrate”) as a support substrate. An n-type cladding layer 13 is laminated on the surface opposite to the substrate, a light emitting layer 14 is laminated on a partial region of the surface of the n-type cladding layer 13 opposite to the substrate, and a surface of the light emitting layer 14 opposite to the substrate is laminated. , p-type cladding layer 15 are stacked, _Mg 2 Ni film on the substrate opposite to the surface of the p-type cladding layer 15, or Pd / _Mg 2 Ni film 16 is laminated, on the substrate surface opposite _Mg 2 Ni film 16 A transparent conductive material 17 is laminated, and a p-type electrode 20 is laminated on the end of the transparent conductive material 17 on the surface opposite to the substrate. In the nitride semiconductor light emitting diode 10 </ b> A, an n-type electrode 19 is laminated on another region of the n-type cladding layer 13 on the surface opposite to the substrate.

The Si substrate 11 is preferably made of, for example, single crystal silicon having a diameter of 3 inches and a thickness of 600 μm, and the crystal orientation of the main surface is preferably (111). The lattice constant (unit: 10 ⁻¹⁰ m) is 3.84 for Si (111) substrate, 3.18 for GaN, and 3.11 for AlN. Since the domain mismatch between the Si (111) substrate and AlN is as small as about 1%, high quality heteroepitaxial growth is possible. The support substrate is preferably a (0001) plane sapphire substrate when it is a sapphire substrate, and is preferably a (0001) plane SiC substrate when it is a SiC substrate.

The buffer layer 12 is deposited on the substrate with a composition of, for example, Al _x Ga _1-x N (0 ≦ x ≦ 1), and the difference between the lattice constant and the thermal expansion coefficient between the Si substrate 11 and the n-type cladding layer 13 is. Is a multilayer film that is laminated in order to alleviate the above, and includes AlN where x = 1. The thermal expansion coefficient (unit: 10 ⁻⁶ / K) at room temperature is 3.59 for silicon, 5.59 for GaN, and 4.15 for AlN. The thermal expansion coefficient at room temperature is GaN> AlN, but at the crystal growth temperature (1400 K), GaN is 5.396 and AlN is 6.942, so GaN <AlN.

  The n-type cladding layer 13 is a Si-doped GaN layer and is referred to as an n-GaN layer. The p-type cladding layer 15 is a Mg-doped GaN layer and is referred to as a p-GaN layer. GaN usually has a wurtzite crystal structure and is represented by a hexagonal crystal lattice.

  The light emitting layer 14 is an active layer having a multiple quantum well structure having a plurality of quantum well layers, and can emit brighter and brighter light than the bulk type. The light emitting layer 14 usually has a multi quantum well (MQW) structure including an InGaN well layer and a GaN or InGaN barrier layer. In a quantum well structure, a layer of a material having a small band gap in which electrons and holes are confined is called a well layer, and a layer of a material having a large band gap that acts as a wall for electrons and holes is called a barrier layer. .

  The n-type electrode 19 and the p-type electrode 20 are Ti / Al laminated electrodes. The metal electrodes 19 and 20 can be deposited by the same process and formed by lift-off by using the same Ti or Al material.

FIG. 2 is a band diagram for explaining a pn junction and an ohmic junction.
LED is configured at the pn junction, p-type electrode are connected by φ _m1> χ + E _G, ohmic by n-type electrode is connected by φ _{m2 <χ,} p-type electrode, and the n-type electrode both Be joined.
Here, phi _m1 is the energy of the vacuum level of the p-type electrode material to the Fermi level E _F, phi _{m @ 2} is an energy from the vacuum level of the n-type electrode material to the Fermi level E _F , chi is the energy from the vacuum level to the conduction band of the semiconductor E _C, E _G is the energy of the semiconductor forbidden band.
However, in a nitride semiconductor light emitting diode, a p-type electrode material having a high work function φm is required for bonding to p-GaN. In this respect, nickel (Ni) has a work function as high as about 5.2 eV, so that the Schottky barrier energy difference between p-GaN and the unstable ITO (4.1 to 4.7 eV) is reduced. And aim for ohmic nature.

  By the way, Mg is generally used as a dopant for p-GaN. Usually, annealing is performed at a temperature of about 800 to 1000 ° C. to desorb hydrogen bonded to Mg. However, since the temperature is near the growth temperature of GaN, nitrogen in GaN is also desorbed, and the surface is roughened or the performance as an LED is deteriorated. Moreover, even in this process, the activation rate of the Mg dopant was as low as 10%, and carriers corresponding to the doping amount could not be produced.

Therefore, the inventors focused on Mg ₂ Ni, which is a hydrogen storage alloy and has a larger amount of hydrogen uptake than other alloys. This Mg ₂ Ni is considered preferable in that Mg, which is one component, is already included as a p-GaN dopant material, and Ni, which is the other component, is a material often used as a p-type electrode.

FIG. 3 is a graph showing the relationship between the light transmittance and wavelength of the Mg ₂ Ni / ITO electrode. The vertical axis represents the light transmittance [%], and the horizontal axis represents the light wavelength [nm]. This Mg ₂ Ni / ITO electrode is formed by laminating Mg ₂ Ni with a thickness of 1 nm and ITO with a thickness of 300 nm on a sapphire substrate, and the annealing temperature is 600 ° C. Its transmittance is 80% or more in the visible light region, and Mg ₂ Ni is easily adapted as a transparent electrode of p-GaN. In the third embodiment, both Pd and Mg ₂ Ni have a thickness of 1 nm.

FIG. 4 is a flowchart showing the manufacturing process of the first embodiment.
Hereinafter, the manufacturing process of the nitride semiconductor light emitting diode 10A will be described with reference to the flowchart of FIG. 4 and FIGS.
(S10) First, an LED structure as shown in FIG. 5 is fabricated by MOCVD. The produced LED structure substrate is a (111) -plane Si substrate (or sapphire substrate or SiC substrate) 11 as a support substrate, and metal organic chemical vapor deposition (MOCVD) on the surface thereof. It is composed of a laminated buffer layer 12, an n-type cladding layer 13 epitaxially grown on the surface, a light emitting layer 14 laminated on the surface, and a p-type cladding layer 15 grown on the surface with a primary crystal. ing. The p-type cladding layer 15 is a Mg-doped p-GaN layer. Note that the p-type cladding layer 15 is not only a p-GaN layer but also an AlGaN layer in many cases.

The n-type cladding layer 13 is a Si-doped n-GaN layer, and GaN uses, for example, trimethyl gallium (TMG) and ammonia (NH ₃ ) as a source gas, and nitrogen (N ₂ ) or hydrogen ( Epitaxial growth is performed using H ₂ ) as a carrier gas.

(S12) Next, as shown in the element cross-sectional view of FIG. 6, the LED structure substrate (laminated substrate) fabricated in S10 has the Mg ₂ Ni film 16A formed on the surface of the p-type cladding layer 15 opposite to the substrate. Then, activation annealing is performed in a rapid annealing furnace. Here, the Mg ₂ Ni film 16A is deposited to an arbitrary thickness, for example, 250 nm to 350 nm (preferably 300 nm). The deposition of 300 nm of the Mg ₂ Ni film 16A uses sputtering, the AC power is 150 W, and the deposition time is 8 minutes and 1 second.

The activation annealing conditions are 400 to 760 ° C. and 3 minutes in a nitrogen atmosphere. With activation annealing, hydrogen contained in the source gas ammonia (NH ₃ ) or Mg acceptor deactivated by bonding with hydrogen of the carrier gas is separated from the hydrogen atoms by heat treatment in a nitrogen atmosphere, It is to activate the acceptor. Here, since the Mg ₂ Ni film 16A occludes the separated hydrogen, the carriers are efficiently activated.

(S14) Next, as shown in the element cross-sectional view of FIG. 7, the Mg ₂ Ni film 16A is removed with hydrofluoric acid from the activation-annealed laminated substrate.
(S16) Next, as shown in the element cross-sectional view of FIG. 8, a new Mg ₂ Ni film 16 and a transparent conductive material 17 are deposited on the laminated substrate from which the Mg ₂ Ni film 16A has been removed. Here, the new Mg ₂ Ni film 16 is deposited to a thickness of 1 nm and has a high transmittance.

An ITO film as a transparent electrode is deposited on the surface of the Mg ₂ Ni film 16 opposite to the substrate. The transparent conductive material 17 (ITO) is deposited to 300 nm by vapor deposition or sputtering. In the case of the flip chip structure, Ni, Mg ₂ Ni, and Pd / Mg ₂ Ni films of opaque electrodes are deposited instead of ITO.

(S18) Next, the first patterning step shown in FIG. 9 is performed on the laminated substrate on which the transparent conductive material 17 is deposited. In this step, the surface of the laminated substrate on which the transparent conductive material 17 (ITO) is deposited is divided into a light emitting region, an n-type electrode region, and a p-type electrode region, and a resist 18 is applied to the light emitting region and the p-type electrode region. It is a process.

(S20) Next, the dry etching process shown in FIG. 10 is performed on the laminated substrate coated with the resist 18.
This step is a step of removing a region where the resist 18 is not applied (that is, the n-type electrode region) up to a part of the n-type cladding layer 13 to form a so-called MESA structure. Dry etching includes, for example, an inductively coupled reactive ion etching method using chlorine (Cl ₂ ) or boron trichloride (BCl ₃ ) gas.

(S22) Next, the second patterning process shown in FIG. 11 is performed on the laminated substrate subjected to the dry etching. This step is a step of applying a photoresist to the light emitting region where the transparent conductive material 17 is laminated and a part of the n-type electrode region.
(S24) Next, the p-type electrode deposition step shown in FIG. 12 is performed on the laminated substrate on which the second patterning has been performed. This step is a step of depositing a Ti / Al laminated film on the p-type electrode region and the surface of the applied photoresist.

(S26) Next, the lift-off process shown in FIG. 13 is performed on the laminated substrate on which the p-type electrode is deposited. In this step, the p-type electrode 20 is formed in the p-type electrode region and the n-type electrode 19 is formed in another region of the n-type electrode region by peeling off the photoresist and Ti / Al deposited on the photoresist. It is a process to do. The electrode can be deposited by sputtering or vacuum evaporation.

(S28) Next, the light emitting diode on which the electrode is formed by lift-off is annealed for 3 minutes in an N ₂ atmosphere at 450 ° C. to 700 ° C. using RTA (Rapid Thermal Annealing). The annealing temperature may be 450 ° C. or higher. However, as will be described later, it is preferably less than 760 ° C., which is a condition for the Mg ₂ Ni film to become a solid phase. In addition, when forming the ITO film at, for example, about 250 ° C., annealing may not be necessary.

As described above, according to the present embodiment, the Mg ₂ Ni film 16A, which is a hydrogen storage material, is formed on the surface of the p-type cladding layer (p-GaN layer) 15 opposite to the substrate (surface opposite to the light emitting layer 14). Since the Mg activation annealing was performed after depositing (S12), the Mg ₂ Ni film 16A absorbs the dissociated hydrogen, and the Mg activation annealing is efficiently performed. Further, after removing the Mg ₂ Ni film 16A, new Mg ₂ Ni film and ITO film are formed. As a result, the Mg ₂ Ni film 16A adsorbs hydrogen, while the Schottky barrier is lowered and the transmittance is increased.

FIG. 14 is a phase diagram of Mg—Ni (see the HANDBOOK of BINARY PHASE DIAGRAMS by WGMoffatt). This figure shows that when Ni is less than 33 atomic% and less than 506 ° C., it becomes a mixed substance of Mg and Mg ₂ Ni, and when Ni is more than 33 atomic% and less than 760 ° C., it becomes a mixed substance of MgNi ₂ and Mg ₂ Ni. When the temperature is higher than these temperatures, the liquid phase is included. In other words, the composition region in which Mg ₂ Ni can exist as an alloy (solid phase) is a major feature of the material proposed in this case that Ni is one point in the vicinity of 33 atomic%. Except for this condition, cracks occur, the composition is not uniform, and the hexagonal crystal is removed, making it difficult to occlude hydrogen.

In other words, in the vicinity of Ni exceeding 33 atomic% (for example, exceeding 33 atomic% to 40 atomic%, preferably 35 atomic%), the Mg activation annealing temperature needs to be less than 760 ° C. In the vicinity of less than 33 atomic percent (for example, less than 33 atomic percent to 25 atomic percent, preferably 30 atomic percent), the Mg activation annealing temperature needs to be less than 506 ° C. In the Mg / Ni laminated structure, Mg ₂ Ni cannot be alloyed.

FIG. 15 is a diagram for explaining how dropout occurs when activation annealing is performed without stacking Mg ₂ Ni films. If the activation annealing is performed at a high temperature (900 ° C.), this temperature is close to the growth temperature (1100 ° C.) of the p-GaN layer (p-type cladding layer 15). A lett appears, the surface becomes rough and the crystallinity deteriorates. On the other hand, in the configuration of the embodiment, since the Mg activation annealing is performed at a low temperature of less than 760 ° C. or less than 506 ° C., no Ga dropout occurs. The photograph shown in FIG. 15 is a photograph of the surface of the Mg ₂ Ni film taken with an AFM (Atomic Force Microscope).

(Second Embodiment)
The first embodiment is configured such that light is transmitted through the transparent conductive material (ITO) 17, but has a flip chip structure that transmits the sapphire substrate 11 side, and an arbitrary gap between the Mg ₂ Ni film and the p-type cladding layer. Pd / Mg ₂ Ni film can be used as it is as a metal electrode by inserting palladium Pd having a thickness (for example, 250 nm to 350 nm, preferably 300 nm).

As described in Non-Patent Document 2, palladium Pd is a material through which hydrogen easily permeates due to the proton effect. For this reason, even if palladium Pd is interposed between the Mg ₂ Ni film and the p-type cladding layer, the hydrogen atoms dissociated from the p-type cladding layer can be occluded by the Mg ₂ Ni film. In addition, palladium Pd has a large work function and has a small difference from the ionization potential of p-GaN, and can supply current to the LED more efficiently than other electrode materials.

Hereinafter, the manufacturing process of the nitride semiconductor light emitting diode 10B (FIG. 21) will be described with reference to the flowchart of FIG. 16 and FIGS. 17 to 21.
(S32) First, as in FIG. 5, the LED structure is formed by MOCVD. Then, as shown in FIG. 17, a resist 18 is applied and patterning is performed.

(S34) Next, the Pd / Mg ₂ Ni film deposition step shown in FIG. 18 is performed.
Mg ₂ Ni or Pd / Mg ₂ Ni is deposited to an arbitrary thickness on the surface of the p-type cladding layer 15 opposite to the substrate. Here, in the case of Pd / Mg ₂ Ni, palladium is deposited on the surface of the p-type cladding layer 15, and Mg ₂ Ni is deposited on the surface. For example, Pd: 0.5 nm to 1.5 nm, preferably 1 nm, Mg ₂ Ni: 250 nm to 350 nm, preferably 300 nm. Pd with a thickness of 1 nm has an AC power of 15 W and a deposition time of 24 seconds, and Mg ₂ Ni with a thickness of 300 nm has an AC power of 150 W and a deposition time of 8 minutes and 1 second.

(S36) Next, the patterning step shown in FIG. 19 is performed. In this step, the plane of the laminated substrate on which the transparent conductive material 17 (ITO) is deposited is divided into a light emitting region, an n-type electrode region, and a p-type electrode region, and a resist 18 is applied to the light emitting region and the p-type electrode region. It is a process.

(S38) Next, the dry etching process shown in FIG. 20 is performed on the laminated substrate coated with the resist 18. This step is a step of removing a region where the resist 18 is not applied (that is, the n-type electrode region) up to a part of the n-type cladding layer 13 to form a so-called MESA structure. Dry etching includes, for example, an inductively coupled reactive ion etching method using chlorine (Cl ₂ ) or boron trichloride (BCl ₃ ) gas.

(S40) Next, the p-type electrode deposition step shown in FIG. 21 is performed on the laminated substrate subjected to the dry etching. In this step, a Ti / Al laminated film is deposited on the p-type electrode region and the surface of the applied photoresist.

(Third embodiment)
In the first embodiment, a Mg ₂ Ni film having a thickness of 1 nm and an ITO film are deposited to improve translucency, and in the second embodiment, Pd having a thickness of 1 nm is interposed to form a thickness of 300 nm. The Mg ₂ Ni film was used as a non-translucent electrode. However, the thickness of Pd was 0.5 nm, the thickness of the Mg ₂ Ni film was 1 nm, and an ITO film was further deposited by 300 nm. It can also be a photoelectrode.

Hereinafter, the manufacturing process of the nitride semiconductor light emitting diode will be described with reference to the flowchart of FIG. 22 and FIGS. 22 to 26.
(S42) First, as in FIG. 5, the LED structure is formed by MOCVD. Then, as shown in FIG. 17, a resist 18 is applied and patterning is performed.
(S44) Next, as shown in the element cross-sectional view of FIG. 23, the laminated substrate having the LED structure is patterned with a resist 18 on the surface of the p-type cladding layer 15.

(S46) Next, as shown in FIG. 24, a Pd / Mg ₂ Ni film 16B is first deposited on the patterned laminated substrate.
That is, in the laminated substrate, palladium having a thickness of 0.5 nm is deposited on the surface of the p-type cladding layer 15 opposite to the substrate, and a Mg ₂ Ni film having a thickness of 1 nm is deposited on the surface of the palladium opposite to the substrate. At this time, Pd is deposited with an AC power of 15 W and a deposition time of 12 seconds, and Mg ₂ Ni is deposited with an AC power of 15 W and a deposition time of 24 seconds.

(S48) The transparent conductive material 17 is further deposited on the laminated substrate on which the Mg ₂ Ni film 16 is deposited, as shown in FIG. That is, in the laminated substrate, the transparent conductive material 17 having a thickness of 300 nm is deposited on the surface of the Mg ₂ Ni film opposite to the substrate. At this time, ITO as the transparent conductive material 17 is deposited with an AC power of 150 W and a deposition time of 15 minutes and 58 seconds.

(S50) The laminated substrate on which the transparent conductive material 17 is deposited is coated with a resist 18 and patterned.
(S52) The patterned laminated substrate is dry etched up to the n-GaN layer (n-type cladding layer 13) as shown in FIG. Then, as shown in FIG. 11, patterning is performed with a photoresist, Ti / Al is deposited on the surface of the transparent conductive material 17 as shown in FIG. 12, and n-type is formed by lift-off as shown in FIG. The electrode 19 and the p-type electrode 20 are formed (S54), and annealed for 3 minutes in an N ₂ atmosphere at 450 to 760 ° C. using an RTA (rapid annealing apparatus).

  In addition, if it is a process like 2nd Embodiment or 3rd Embodiment, since it is not necessary to anneal twice like 1st Embodiment, it will also lead to process shortening.

(Fourth embodiment)
In the first embodiment, after the Mg ₂ Ni film 16A is formed and activation annealing is performed (S12), the Mg ₂ Ni film 16A is removed with hydrofluoric acid (S14), and a new Mg ₂ Ni film is formed. 16 is formed (S16), but the LED functions even when the Mg ₂ Ni film 16A is removed with hydrofluoric acid.

A manufacturing process of the nitride semiconductor light emitting diode will be described with reference to FIG.
In the fourth embodiment, as in the first embodiment, the LED structure is formed by MOCVD (S60), an Mg ₂ Ni film is formed, activation annealing is performed (S62), and Mg ₂ Ni is used with hydrofluoric acid. The film is removed (S64). Next, the stacked element from which the Mg ₂ Ni film has been removed is subjected to patterning (S66), dry etching (S68), patterning (S70), p-type electrode deposition (S72), lift-off (S74), and annealing (S76). ), A nitride semiconductor light emitting diode (see FIG. 28) is fabricated. The conventional nitride semiconductor light emitting diode 10C is similar in structure, but differs in that the Mg activation of the p-type cladding layer 15 is performed efficiently.

(Modification)
The present invention is not limited to the embodiments described above, and various modifications such as the following are possible.
(1) In the above embodiment, an ITO film is used as the transparent conductive material 17, but instead of the ITO film, ZnO, AZO (aluminum doped zinc oxide), GZO (gallium doped zinc oxide), IZO (registered trademark). Similar effects can be obtained with (indium-doped zinc oxide), TiO ₂ (titanium dioxide), or the like. In the above embodiment, GaN is used as the main raw material of the LED, but GaAs, InP, or the like can be used instead of GaN.
(2) In the above embodiment, a single light emitting diode has been described, but a plurality of nitride semiconductor light emitting diodes 10A and 10B can be two-dimensionally arranged on the Si substrate 11 to form a display device.

10A, 10B, 10C Nitride semiconductor light emitting diode 11 Si substrate, sapphire substrate, or SiC substrate 12 Buffer layer 13 n-type cladding layer 14 light-emitting layer 15 p-type cladding layer (p-GaN layer)
16, 16A Mg ₂ Ni film 16B Pd / Mg ₂ Ni film 17 Transparent conductive material 18 Resist 19 N-type electrode 20 P-type electrode

Claims (9)

A nitride semiconductor light emitting diode comprising a light emitting layer and a p-GaN layer stacked on the surface of the light emitting layer,
A nitride semiconductor light emitting diode comprising an Mg ₂ Ni layer laminated on the surface of the p-GaN layer opposite to the light emitting layer. The nitride semiconductor light-emitting diode according to claim 1,
A nitride semiconductor light-emitting diode, wherein a palladium layer is interposed between the Mg ₂ Ni layer and the p-GaN layer. The nitride semiconductor light-emitting diode according to claim 1 or 2,
The Mg ₂ Ni layer has a Ni ratio exceeding 33 atomic% to 40 atomic%,
The nitride semiconductor light emitting diode according to claim 1, wherein the p-GaN layer is subjected to Mg activation annealing at less than 760 ° C. The nitride semiconductor light-emitting diode according to any one of claims 1 to 3,
A nitride semiconductor light-emitting diode, wherein a transparent conductive film is laminated on a surface of the Mg ₂ Ni layer opposite to the light-emitting layer. The nitride semiconductor light-emitting diode according to claim 4,
The nitride semiconductor light-emitting diode, wherein the Mg ₂ Ni layer has a thickness of 0.5 nm to ₂ nm. The nitride semiconductor light-emitting diode according to claim 2,
The Mg ₂ Ni layer has a thickness of 0.5 nm to 1.5 nm,
The palladium layer has a thickness of 250 nm to 350 nm,
The light emitted from the light emitting layer is emitted from a substrate on which the light emitting layer is laminated. A method for manufacturing a nitride semiconductor light emitting diode comprising a light emitting layer and a p-GaN layer laminated on the surface of the light emitting layer,
A step of laminating a Mg ₂ Ni layer on the surface of the p-GaN layer opposite to the light emitting layer;
The method of manufacturing a nitride semiconductor light-emitting diode, comprising: a step of annealing the p-GaN layer for Mg activation. A method for producing a nitride semiconductor light emitting diode according to claim 7,
A method of manufacturing a nitride semiconductor light emitting diode, comprising: removing the Mg ₂ Ni layer after the p-GaN layer is annealed for Mg activation. A method for manufacturing a nitride semiconductor light-emitting diode according to claim 8,
A method for manufacturing a nitride semiconductor light emitting diode, comprising a step of laminating a new Mg ₂ Ni layer on the surface of the p-GaN layer opposite to the light emitting layer.