JP2017112313A - Ultraviolet light-emitting device and method of manufacturing ultraviolet light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultraviolet light-emitting device capable of reducing contact resistance between an n-type nitride semiconductor layer and a first electrode part, and a method of manufacturing the same.SOLUTION: The ultraviolet light-emitting device includes: an n-type nitride semiconductor layer 20; a first electrode part 30 containing Ti, Al, Ni and Au as constituent elements, having an AlNi alloy part, and provided on the n-type nitride semiconductor layer 20; a p-type nitride semiconductor layer 50; and a light-emitting layer 40 positioned between the n-type nitride semiconductor layer 20 and the p-type nitride semiconductor layer 50. When a portion including the AlNi alloy part of the first electrode part 30 is viewed cross-sectionally, the average distance between the n-type nitride semiconductor layer 20 and the AlNi alloy part is 20 nm or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ultraviolet light emitting device and a method for manufacturing the ultraviolet light emitting device.

  Ultraviolet light emitting devices are applied in various fields by taking advantage of their small size and low power consumption. As disclosed in Patent Document 1, generally, an ultraviolet light emitting device includes an n-type nitride semiconductor layer, a light emitting layer, and a stacked portion having a p-type nitride semiconductor layer. In this ultraviolet light emitting device, ultraviolet light is emitted from the light emitting layer by electric power supplied via one electrode portion on the n-type nitride semiconductor layer and the other electrode portion on the p-type nitride semiconductor layer. The

International Publication 2012/144046 Pamphlet JP 2015-43468 A

  From the viewpoint of further reducing power consumption by reducing the forward voltage Vf, it is important to reduce the contact resistance between the stacked portion and the electrode portion thereon. However, in the conventional ultraviolet light emitting device, the contact resistance is not sufficiently reduced. In particular, the fact is that little attention has been paid to the contact resistance between the n-type nitride semiconductor layer and the electrode portion thereon. For example, in Patent Document 1, a four-layer metal layer of Ti / Al / Ti / Au is sequentially deposited with a film thickness of 20 nm / 100 nm / 50 nm / 100 nm, and heat treatment is applied by RTA (instantaneous thermal annealing) or the like, A method for forming an n-electrode on an n-type nitride semiconductor layer is disclosed. In Patent Document 2, a four-layer metal layer of Tl / Al / Ti / Au is sequentially deposited with a film thickness of 20 nm / 100 nm / 20 nm / 200 nm, and a heat treatment by RTA treatment (900 ° C., 1 minute) is added, A method for forming an n-electrode is disclosed.

However, as can be seen from the reference examples described later, it cannot be said that the contact resistance between the n-type nitride semiconductor layer and the n electrode of the ultraviolet light emitting device obtained by this method is sufficiently low.
Therefore, the present invention has been made in view of such circumstances, and an ultraviolet light emitting device capable of reducing the contact resistance between the n-type nitride semiconductor layer and the first electrode portion, and a method for manufacturing the same. The purpose is to provide.

  An ultraviolet light emitting device according to an aspect of the present invention includes an n-type nitride semiconductor layer, Ti, Al, Ni, and Au as constituent elements, an AlNi alloy portion, and on the n-type nitride semiconductor layer. A first electrode portion provided; a p-type nitride semiconductor layer; and a light-emitting layer positioned between the n-type nitride semiconductor layer and the p-type nitride semiconductor layer, the first electrode portion When the portion including the AlNi alloy part is viewed in cross section, an average distance between the n-type nitride semiconductor layer and the AlNi alloy part is 20 nm or more.

  An ultraviolet light emitting device according to another aspect of the present invention includes an n-type nitride semiconductor layer, Ti, Al, Ni, and Au as constituent elements, an AlNi alloy portion, and on the n-type nitride semiconductor layer. A first electrode portion provided on the first electrode portion; a p-type nitride semiconductor layer; and a light emitting layer provided between the n-type nitride semiconductor layer and the p-type nitride semiconductor layer. An average interval between the AlNi alloy parts is 100 nm or more and 2500 nm or less when a portion of the electrode part including the AlNi alloy part is viewed in cross section.

  The manufacturing method of the ultraviolet light-emitting device which concerns on 1 aspect of this invention WHEREIN: Between an n-type nitride semiconductor layer, a p-type nitride semiconductor layer, the said n-type nitride semiconductor layer, and the said p-type nitride semiconductor layer Ti is formed to a thickness of 5 nm or more and 40 nm or less on the n-type nitride semiconductor layer of the semiconductor wafer including a light emitting layer positioned on the substrate, and Al is formed to a thickness of 160 nm or more and 270 nm or less on the Ti. A deposition step of forming Ni on the Al to a thickness of 5 nm to 50 nm and forming Au on the Ni to a thickness of 40 nm to 100 nm; and an annealing step for heat treatment after the deposition step; It is characterized by providing.

  An ultraviolet light emitting device manufacturing method according to another aspect of the present invention includes an n-type nitride semiconductor layer, a p-type nitride semiconductor layer, the n-type nitride semiconductor layer, and the p-type nitride semiconductor layer. Ti is formed to a thickness of 5 nm to 40 nm on the n-type nitride semiconductor layer of the semiconductor wafer having a light emitting layer positioned therebetween, Al is formed on the Ti, and Ni is formed on the Al. A deposition step of forming Au on the Ni to a thickness of 40 nm or more and 100 nm or less, and an annealing step of performing a heat treatment after the deposition step. In the deposition step, the Al and Ni The Al and the Ni are formed so that the film thickness ratio (Al film thickness / Ni film thickness) satisfies 5 or more and 9.4 or less.

An ultraviolet light emitting device manufacturing method according to yet another aspect of the present invention includes an n-type nitride semiconductor layer, a p-type nitride semiconductor layer, the n-type nitride semiconductor layer, and the p-type nitride semiconductor layer. Ti is formed to a thickness of 5 nm or more and 40 nm or less on the n-type nitride semiconductor layer of the semiconductor wafer including a light emitting layer positioned between the layers, Al is formed on the Ti, and Ni is formed on the Al. Is deposited to a thickness of 5 nm to 50 nm and Au is formed on the Ni, and an annealing process is performed after the deposition process, and in the deposition process, the Al and Au The Al and the Au are formed so that the film thickness ratio (Al film thickness / Au film thickness) satisfies 2.8 or more and 5 or less.
The summary of the invention does not enumerate all the features of the present invention. In addition, a sub-combination of these feature groups can also be an invention.

  According to one embodiment of the present invention, it is possible to provide an ultraviolet light emitting device capable of reducing contact resistance between an n-type nitride semiconductor layer and a first electrode portion, and a method for manufacturing the same.

It is sectional drawing which shows typically the structural example of the ultraviolet-light-emitting device 100 which concerns on embodiment of this invention. It is a cross-sectional TEM image of a 1st electrode part. 3 is a cross-sectional TEM image showing each constituent element based on the surface analysis result of FIG. 2. 2 is a cross-sectional TEM image of a first electrode portion obtained in Example 1. FIG. 2 is a cross-sectional TEM image of a first electrode portion obtained in Example 1. FIG. 2 is a cross-sectional TEM image of a first electrode portion obtained in Example 1. FIG. 4 is a cross-sectional TEM of a first electrode portion obtained in Example 2. 4 is a cross-sectional TEM of a first electrode portion obtained in Example 2. 4 is a cross-sectional TEM of a first electrode portion obtained in Example 2. 2 is a cross-sectional TEM image of a first electrode portion obtained in Reference Example 1. 2 is a cross-sectional TEM image of a first electrode portion obtained in Reference Example 1. 2 is a cross-sectional TEM image of a first electrode portion obtained in Reference Example 1. 6 is a cross-sectional TEM image of a first electrode portion obtained in Reference Example 2. 14 is a cross-sectional TEM image showing each constituent element based on the surface analysis result of FIG. 13.

  Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

<Ultraviolet light emitting device>
FIG. 1 is a cross-sectional view schematically showing a configuration example of an ultraviolet light emitting device 100 according to an embodiment of the present invention. As shown in FIG. 1, the ultraviolet light emitting device 100 includes an n-type nitride semiconductor layer 20, a first electrode unit 30 provided on the n-type nitride semiconductor layer 20, a p-type nitride semiconductor layer 50, and A light emitting layer 40 located between the n-type nitride semiconductor layer 20 and the p-type nitride semiconductor layer 50. The first electrode unit 30 includes Ti, Al, Ni, and Au as constituent elements and has an AlNi alloy part.
In the ultraviolet light emitting device 100, as will be described later with reference to FIG. 4, the n-type nitride semiconductor layer 20 and the AlNi alloy when the portion including the AlNi alloy portion of the first electrode portion 30 is viewed in cross section. The average distance from the part is 20 nm or more.
Further, in this ultraviolet light emitting device 100, as will be described later with reference to FIG. 5, when the part including the AlNi alloy part of the first electrode part 30 is viewed in cross section, the average interval between the AlNi alloy parts is It is 100 nm or more and 2500 nm or less.

In the embodiment shown in FIG. 1, the n-type nitride semiconductor layer 20, the light emitting layer 40, and the p-type nitride semiconductor layer 50 are stacked in this order from the substrate 10 side, but the present invention is not limited to this. . In the present invention, for example, the p-type nitride semiconductor layer 50, the light emitting layer 40, and the n-type nitride semiconductor layer 20 may be stacked in this order from the substrate 10 side. The embodiment shown in FIG. 1 is a horizontal ultraviolet light emitting device in which a part of the n-type nitride semiconductor layer 20, the light emitting layer 40, and the p type nitride semiconductor layer 50 have a mesa structure. Not limited to. The present invention may be, for example, a vertical ultraviolet light emitting device. In the case of a vertical ultraviolet light emitting device, it is preferable from the viewpoint of improving luminous efficiency that the substrate is peeled off.
Hereinafter, each component constituting the ultraviolet light emitting device 100 will be described with specific examples.

<Board>
The substrate 10 is not particularly limited as long as an n-type nitride semiconductor layer can be formed thereon. Specific examples of the substrate 10 include sapphire, Si, SiC, MgO, Ga ₂ O ₃ , ZnO, GaN, InN, AlN, and mixed crystal substrates thereof. Difference in lattice constant with the n-type nitride semiconductor layer formed on the upper layer side of the substrate 10 is small, so that the threading dislocation can be reduced by growing in a lattice matching system, and the lattice strain for generating the hole gas can be increased. The substrate 10 is a single crystal substrate having a bulk of a nitride semiconductor such as GaN, AlN, or AlGaN, or a nitride semiconductor layer (also referred to as a template) of GaN, AlN, AlGaN, or the like grown on a certain material. It is preferable to use it. Further, the substrate 10 may be mixed with impurities.

<N-type nitride semiconductor layer>
The n-type nitride semiconductor layer 20 may be formed directly on the substrate 10 as shown in FIG. Further, a layer other than the n-type nitride semiconductor layer 20 may be formed on the substrate 10, and the n-type nitride semiconductor layer 20 may be formed thereon. For example, a buffer layer may be formed on the substrate 10, an n-type AlGaN layer may be formed as the n-type nitride semiconductor layer 20 on the buffer layer, and the light emitting layer 40 may be formed thereon. In another form, the n-type nitride semiconductor layer 20 may be formed directly or indirectly on the light emitting layer 40.
The n-type nitride semiconductor layer 20 is not particularly limited as long as the conductivity type is an n-type nitride semiconductor, but is preferably a mixed crystal of AlN, GaN, and InN from the viewpoint of realizing high luminous efficiency. In addition to the n-type dopant, the n-type nitride semiconductor layer 20 may be mixed with other group V elements such as P, As, and Sb, and impurities such as C, H, F, O, Mg, and Si.

<First electrode part>
The first electrode part 30 is formed on a part of the n-type nitride semiconductor layer 20 and includes Ti, Al, Ni, Au as constituent elements and has an AlNi alloy part. Although not particularly limited, the ultraviolet light emitting device 100 may further include a pad electrode mainly composed of Au, Al, or the like on the first electrode unit 30.
FIG. 2 is a cross-sectional TEM image of the first electrode portion. FIG. 2A is an original TEM image. 2 (b) to 2 (h) are gray scales of the surface analysis results (in order, Al, Ga, N, Ti, O, Ni, Au) of main elements by TEM-EDX in the same field of view as FIG. 2 (a). It is an image. FIG. 3 is a cross-sectional TEM image in which the constituent elements in FIG. 2A are added based on the surface analysis results of the elements in FIGS. 2B to 2H. In this example, AlGaN is formed as an n-type nitride semiconductor layer, and a first electrode portion including a Ti portion, an AlAu portion, an AlNi portion, an AlO portion, and a Ti portion is disposed thereon, and the first electrode portion is disposed on the first electrode portion. It is understood that this is a structure in which pad electrodes made of Au are arranged. Although details will be described later, it can be seen that the AlNi portion is formed at a position away from the AlGaN layer which is the n-type nitride semiconductor layer.

As a first aspect of the present invention, when the portion including the AlNi alloy portion of the first electrode portion is viewed in cross section, the average distance Dv (ave) between the n-type nitride semiconductor layer and the AlNi alloy portion is 20 nm or more. is there. That is, the n-type nitride semiconductor layer 20 and the AlNi alloy part are cut at a cut surface when the first electrode part 30 is cut in a plane parallel to the thickness direction of the first electrode part 30 and passing through the AlNi alloy part. The average distance Dv (ave) is 20 nm or more.
Here, the average distance Dv (ave) between the n-type nitride semiconductor layer and the AlNi alloy part is the result of measuring the distance Dv (see FIG. 3) between the n-type nitride semiconductor layer and the AlNi alloy part at 10 points. Mean means. The average distance Dv (ave) is preferably 30 nm or more, more preferably 40 nm or more. Further, although there is no particular upper limit for Dv (ave), from the viewpoint of production efficiency, Dv (ave) is preferably 400 nm or less, more preferably 300 nm or less, and even more preferably 200 nm or less. .

  As a second aspect of the present invention, the average distance Dh (ave) between the AlNi alloy portions is 100 nm or more and 2500 nm or less when the portion of the first electrode portion including the AlNi alloy portion is viewed in cross section. That is, the average distance Dh (ave) between the AlNi alloy parts is 100 nm on the cut surface when the first electrode part 30 is cut in a plane parallel to the thickness direction of the first electrode part 30 and passing through the AlNi alloy part. The thickness is 2500 nm or less. Here, the average distance Dh (ave) between the AlNi alloy parts means the average of the results of measuring the distance Dh between the AlNi alloy parts at 10 points. The average distance Dh (ave) is preferably 2300 nm or less, and more preferably 2000 nm or less.

<Light emitting layer>
The light emitting layer 40 may be formed directly on the n-type nitride semiconductor layer 20 as shown in FIG. Further, a layer other than the light emitting layer 40 may be formed on the n-type nitride semiconductor, and the light emitting layer 40 may be formed thereon. The formation position of the light emitting layer 40 is not particularly limited. Specifically, an undoped AlGaN layer may be formed on the n-type nitride semiconductor layer 20, and the light emitting layer 40 may be formed thereon. In another form, the light emitting layer 40 may be formed on the p-type nitride semiconductor layer 50. The light emitting layer 40 is not particularly limited as long as it is a nitride semiconductor, but is preferably a mixed crystal of AlN, GaN, and InN from the viewpoint of realizing high light emission efficiency. In addition to N, the light emitting layer 40 may be mixed with other group V elements such as P, As, and Sb, and impurities such as C, H, F, O, Mg, and Si. The light emitting layer 40 may have a quantum well structure or a single layer structure, but preferably has at least one well structure from the viewpoint of realizing high light emission efficiency.

<P-type nitride semiconductor layer>
The p-type nitride semiconductor layer 50 may be formed directly on the light emitting layer 40 as shown in FIG. Further, a layer other than the p-type nitride semiconductor layer 50 may be formed on the light emitting layer 40, and the p-type nitride semiconductor layer 50 may be formed thereon. For example, a gradient composition layer in which the ratio of constituent elements changes continuously or discretely may be formed on the light emitting layer 40, and the p-type nitride semiconductor layer 50 may be formed thereon. The formation position of the p-type nitride semiconductor layer 50 is not particularly limited. The ultraviolet light emitting device 100 may further include a barrier layer having a relatively large band gap between the light emitting layer 40 and the gradient composition layer. In other forms, p-type nitride semiconductor layer 50 may be formed directly or indirectly on substrate 10.

From the viewpoint of generating a two-dimensional hole gas, the p-type nitride semiconductor layer 50 is formed directly on the composition gradient layer, and the composition of the p-type nitride semiconductor layer (Al _y Ga _1-y N) is that of the composition gradient layer. It is preferable that the outermost surface composition Al _x Ga _1-x N has a relationship of 0 ≦ y <x ≦ 1, and the thickness of the p-type nitride semiconductor layer 50 is 1 nm or more and less than 20 nm. From the viewpoint of efficiently generating the two-dimensional hole gas of the composition gradient layer and the p-type nitride semiconductor layer 50, (yx) is preferably 0.1 or more and 0.8 or less, and more preferably 0.2 or more and 0.5 or less. Is preferred. In order to efficiently generate the two-dimensional hole gas between the composition gradient layer and the p-type nitride semiconductor layer 50, the p-type nitride semiconductor is used to distort the p-type nitride semiconductor layer 50 (that is, to reduce the relaxation rate). The thickness of the layer 50 is preferably 1 nm to 10 nm, and more preferably 1 nm to 5 nm.

The electrode may be in direct contact with the p-type nitride semiconductor layer. Further, the p-type nitride semiconductor layer may have a multilayer structure, and in that case, the electrode may be in contact with the uppermost surface of the multilayer structure. The p-type nitride semiconductor layer 50 may contain a p-type dopant from the viewpoint of generating holes in the thin film, or may not contain a dopant in order to inject holes directly into the two-dimensional hole gas at the interface from the electrode. Also good. Mg is generally used as the p-type dopant, but Be, Zn, and the like can be used as long as they are impurities that generate holes.
XRD (X-ray diffraction), EDX (energy dispersive X-ray spectroscopy), XRF (fluorescence X-ray analysis), AES (AES) can be used to confirm the compositional difference between the p-type nitride semiconductor layer 50 and the outermost surface of the graded composition layer. Identification is possible by various analysis methods such as Auger electron spectroscopy, SIMS (secondary ion mass spectrometry), and EELS (electron energy loss spectroscopy).

<Second electrode part>
The ultraviolet light emitting device 100 may further include a second electrode unit from the viewpoint of increasing hole injection efficiency into the p-type nitride semiconductor layer 50. From the viewpoint of efficiently injecting holes into the p-type nitride semiconductor layer 50, the second electrode portion has a metal having a large work function such as Ni, Au, Pt, Ag, Rh, Pd, or an alloy thereof, ITO, An oxide electrode such as is desirable but not limited thereto.
It is preferable that the second electrode portion is arranged so as to overlap at least with the region of the p-type nitride semiconductor layer that is not in contact with the contact electrode when seen in a plan view. In addition to this form, the second electrode part preferably includes a reflective layer that has a higher reflectance with respect to light from the light emitting layer 40 than the contact electrode. The reflective layer is preferably made of a metal such as Ag, Rh, or Al having a high reflectance at a specific wavelength, a reflective film using a dielectric multilayer film, a fluororesin, or the like from the viewpoint of reflecting light emission. However, this is not the case. The reflective layer may be in direct contact with the p-type nitride semiconductor layer 50, or a transparent or semi-transparent layer with respect to the emission wavelength is sandwiched between the p-type nitride semiconductor layer 50 and the reflective layer. May be. For example, transparent ITO may be in contact with the p-type nitride semiconductor layer 50 with respect to the emission wavelength of 400 nm, and Ag having a high reflectance may be in contact with the ITO as a reflective layer.

  The definition of reflectivity is that a contact electrode or reflection layer material to be measured is formed on a transparent material, and light having a peak wavelength of element emission is incident and reflected from the transparent material side with a reflectivity measuring instrument. It refers to the vertical reflectance obtained at the time. For example, a method for confirming a “reflection layer” when a NiAu laminated electrode is used as a contact electrode, Al is used as a reflection layer, and an ultraviolet light emitting device having a wavelength of 265 nm is used is as follows. That is, Al is formed on the sapphire substrate with the same film thickness from the sapphire side when the NiAu laminated electrode is formed on the sapphire substrate that transmits light with a wavelength of 265 nm and light is incident from the sapphire side. If the vertical reflectance when light is incident is high, it can be confirmed that Al is a reflective layer.

Although the manufacturing method of the ultraviolet light-emitting device which concerns on embodiment of this invention is not restrict | limited in particular, It can obtain by the manufacturing method of the ultraviolet light-emitting device mentioned later.
The ultraviolet light emitting device of the present invention can be applied to various devices.
The ultraviolet light emitting device of the present invention can be applied to and replaced by all existing devices in which an ultraviolet lamp is used. In particular, the present invention can be applied to an apparatus using deep ultraviolet light having a wavelength of 280 nm or less.
The ultraviolet light emitting device of the present invention can be applied to, for example, devices in the medical / life science field, the environmental field, the industrial / industrial field, the life / home appliance field, the agricultural field, and other fields.
The ultraviolet light-emitting device of the present invention is a chemical / chemical substance synthesis / decomposition device, liquid / gas / solid (container, food, medical equipment, etc.) sterilizer, semiconductor cleaning device, film / glass / metal surface, etc. Reforming equipment, exposure equipment for manufacturing semiconductors, FPDs, PCBs and other electronic products, printing / coating equipment, adhesion / sealing equipment, transfer / molding equipment for films / patterns / mockups, banknotes / scratches / blood / chemical substances It can be applied to measurement / inspection equipment.

Examples of liquid sterilizers include automatic ice making equipment, ice trays, ice storage containers, water storage tanks for ice making machines, ice making machines, freezers, ice making machines, humidifiers, dehumidifiers, water server cold water tanks, hot water tanks, flow paths Pipes, stationary water purifiers, portable water purifiers, water heaters, water heaters, wastewater treatment devices, disposers, toilet drainage traps, washing machines, dialysis water sterilization modules, peritoneal dialysis connector sterilizers, disaster water storage systems, etc. This is not the case.
Examples of gas sterilizers include air purifiers, air conditioners, ceiling fans, floor and bedding vacuum cleaners, futon dryers, shoe dryers, washing machines, clothes dryers, indoor sterilization lights, and storage ventilation. Examples include, but are not limited to, systems, shoe boxes, and chests.
Examples of solid sterilizers (including surface sterilizers) include vacuum packers, belt conveyors, medical / dental / barber / beauty salon hand tool sterilizers, toothbrushes, toothbrush holders, chopstick boxes, cosmetic pouches, Examples include, but are not limited to, drainage lids, toilet bowl cleaners, toilet lids, and the like.

<Method for manufacturing ultraviolet light emitting device>
In the third aspect of the present invention, the substrate 10, the n-type nitride semiconductor layer 20, the p-type nitride semiconductor layer 50, and the n-type nitride semiconductor layer 20 and the p-type nitride semiconductor layer 50 are interposed. Ti is formed to a thickness of 5 nm to 40 nm on the n-type nitride semiconductor layer 20 of the semiconductor wafer including the light emitting layer 40 positioned, and Al is formed to a thickness of 160 nm to 270 nm on Ti. An ultraviolet ray comprising: a deposition step of forming Ni on Al to a thickness of 5 nm to 50 nm; and forming Au on Ni to a thickness of 40 nm to 100 nm; and an annealing step for heat treatment after the deposition step. It is a manufacturing method of a light-emitting device.

  In the fourth aspect of the present invention, the substrate 10, the n-type nitride semiconductor layer 20, the p-type nitride semiconductor layer 50, and the n-type nitride semiconductor layer 20 and the p-type nitride semiconductor layer 50 are interposed. Ti is formed to a thickness of 5 nm to 40 nm on the n-type nitride semiconductor layer 20 of the semiconductor wafer including the light emitting layer 40 positioned, Al is formed on Ti, Ni is formed on Al, A deposition process for forming Au on Ni to a thickness of 40 nm to 100 nm; and an annealing process for heat treatment after the deposition process. In the deposition process, a film thickness ratio between Al and Ni (Al film thickness / This is a method for manufacturing an ultraviolet light emitting device, in which Al and Ni are formed so that the Ni film thickness satisfies 5 or more and 9.4 or less.

  In the fifth aspect of the present invention, the substrate 10, the n-type nitride semiconductor layer 20, the p-type nitride semiconductor layer 50, and the n-type nitride semiconductor layer 20 and the p-type nitride semiconductor layer 50 are interposed. Ti is formed to a thickness of 5 nm to 40 nm on the n-type nitride semiconductor layer 20 of the semiconductor wafer including the light emitting layer 40 positioned, Al is formed on Ti, and Ni is formed to 5 nm to 50 nm on Al. A deposition step of forming Au on Ni, and an annealing step of heat treatment after the deposition step. In the deposition step, a film thickness ratio of Al to Au (Al film thickness / This is a method for manufacturing an ultraviolet light emitting device, in which Al and Au are formed so that the Au film thickness satisfies 2.8 or more and 5 or less.

In any of the manufacturing methods of the ultraviolet light emitting devices of the third to fifth aspects, the method for forming each component is not particularly limited, and examples thereof include a resistance heating vapor deposition method, an electron beam vapor deposition method, and a sputtering method. .
Any of the third to fifth aspects of the method for manufacturing an ultraviolet light emitting device may further include an etching step for exposing a part of the n-type nitride semiconductor layer 20 before the deposition step. . The etching process may be dry etching or wet etching. The etching step can expose a desired region of n-type nitride semiconductor layer 20 by using a resist formed in a desired pattern as a mask.
In any of the third to fifth aspects of the method for manufacturing an ultraviolet light emitting device, the temperature of the annealing step for heat treatment is not particularly limited, but the heat treatment is exemplified at 600 ° C. or more and 1200 ° C. or less. Further, the time for the annealing step for heat treatment is not particularly limited, but examples include heating for 5 seconds or more and 900 seconds or less.

<Effect of embodiment>
As described in the aforementioned Patent Documents 1 and 2, a four-layer metal layer of Ti / Al / Ti / Au is deposited, and heat treatment is performed by RTA or the like to form an n-electrode on the n-type nitride semiconductor layer. How to do was known. However, none of the documents describes the use of Ni as the material for the n-electrode, and it is common knowledge that the film thickness of Al is about 100 nm.
However, the present inventors diligently studied without being bound by such common sense. As a result, for example, the contact resistance between the n-type nitride semiconductor layer 20 and the first electrode unit 30 is smaller than in the conventional method by the method for manufacturing the ultraviolet light emitting device of the third to fifth aspects described above. An ultraviolet light emitting device having a small forward voltage Vf can be obtained.
Thus, according to the embodiment of the present invention, it is possible to provide an ultraviolet light emitting device capable of reducing the contact resistance between the n-type nitride semiconductor layer and the first electrode portion, and a method for manufacturing the same. The forward voltage Vf can be reduced by reducing the contact resistance between the n-type nitride semiconductor layer and the first electrode portion. Thereby, further reduction in power consumption of the ultraviolet light emitting device can be realized.

<Example 1>
On an AlN substrate obtained from an AlN single crystal, an AlN buffer layer, an n-AlGaN layer, an AlGaN multiple quantum well structure as a light emitting layer, and a p-GaN layer are formed by metal organic vapor phase epitaxy (MOCVD method). Films were formed in this order.
Next, using the resist pattern formed by the photolithography method, dry etching of the p-GaN layer and AlGaN was performed with a chlorine-based gas to expose a part of the n-AlGaN layer.
On a part of the exposed n-AlGaN, Ti 19 nm, Al 210 nm, Ni 34 nm and Au 57 nm were deposited in this order. Subsequently, the 1st electrode part was formed by heat processing for 880 degreeC 120 second. The film thickness ratio between Al and Ni (Al film thickness / Ni film thickness) is 6.2, and the film thickness ratio between Al and Au (Al film thickness / Au film thickness) is 3.7.

Cross-sectional TEM images of the first electrode portion obtained in Example 1 are shown in FIGS. FIG. 4 shows AlNi alloy parts (9 points indicated by arrows) confirmed by TEM-EDX. FIG. 5 shows the distance between the n-AlGaN layer and the AlNi alloy part in each AlNi alloy part. FIG. 6 shows the spacing between the AlNi alloy parts. Since the average distances Dv (ave) and Dh (ave) are calculated based on an average of 10 points, another cross-sectional TEM image is used for the shortage (not shown).
As a result, the average distance Dv (ave) between the n-AlGaN layer, which is an n-type nitride semiconductor layer, and the AlNi alloy part included in the first electrode part was 57 nm. The average distance Dh (ave) between the AlNi alloy parts was 1052 nm.

<Example 2>
A first electrode portion was formed in the same manner as in Example 1 except that Ti was 20 nm, Al was 191 nm, Ni was 32 nm, and Au was 58 nm. The film thickness ratio between Al and Ni (Al film thickness / Ni film thickness) is 6.0, and the film thickness ratio between Al and Au (Al film thickness / Au film thickness) is 3.3.
Sectional TEM images of the first electrode portion obtained in Example 2 are shown in FIGS. FIG. 7 shows AlNi alloy parts (seven points indicated by arrows) confirmed by TEM-EDX. FIG. 8 shows the distance between the n-AlGaN layer and the AlNi alloy part in each AlNi alloy part. FIG. 9 shows the spacing between the AlNi alloy parts. Since the average distances Dv (ave) and Dh (ave) are calculated by an average of 10 points, other cross-sectional TEM images were used for the shortage.
As a result, the average distance Dv (ave) between the n-AlGaN layer, which is an n-type nitride semiconductor layer, and the AlNi alloy part included in the first electrode part was 101 nm. Further, the average distance Dh (ave) between the AlNi alloy parts was 337 nm.

<Reference Example 1>
A first electrode portion was formed in the same manner as in Example 1 except that Ti was 19 nm, Al was 142 nm, Ni was 36 nm, and Au was 71 nm. The film thickness ratio between Al and Ni (Al film thickness / Ni film thickness) is 3.9, and the film thickness ratio between Al and Au (Al film thickness / Au film thickness) is 2.0.
Cross-sectional TEM images of the first electrode portion obtained in Reference Example 1 are shown in FIGS. FIG. 10 shows AlNi alloy parts (three points indicated by arrows) confirmed by TEM-EDX. FIG. 11 shows the distance between the n-AlGaN layer and the AlNi alloy part in each AlNi alloy part. FIG. 12 shows the spacing between the AlNi alloy parts. Since the average distances Dv (ave) and Dh (ave) are calculated by an average of 10 points, other cross-sectional TEM images were used for the shortage.
As a result, the n-AlGaN layer, which is an n-type nitride semiconductor layer, and the AlNi alloy part included in the first electrode part are adjacent to each other via only the 10 nm Ti layer, and therefore the average distance Dv (ave) Was 10 nm. The average distance Dh (ave) between AlNi alloy parts was 2805 nm.

<Reference Example 2>
A first electrode portion was formed in the same manner as in Example 1 except that Ti was 20 nm, Al was 286 nm or more, Ni was 30 nm, and Au was 57 nm. The film thickness ratio between Al and Ni (Al film thickness / Ni film thickness) is 9.5, and the film thickness ratio between Al and Au (Al film thickness / Au film thickness) is 5.0.
FIG. 13 is a cross-sectional TEM image of the first electrode portion obtained in Reference Example 2. FIG. 13A is an original TEM image. FIGS. 13B to 13H are gray scales of surface analysis results (in order, Al, Ga, N, Ti, O, Ni, Au) of main elements by TEM-EDX in the same field of view as FIG. 13A. It is an image. FIG. 14 is a cross-sectional TEM image showing the constituent elements of FIG. 13A based on the surface analysis results of the elements of FIGS. 13B to 13H.
As a result, the first electrode portion was different from the AlNi alloy state so far, and an AlNiAu alloy portion containing Al, Ni, and Au was formed. In addition, the n-AlGaN layer, which is an n-type nitride semiconductor layer, and the AlNiAu alloy part included in the first electrode part were in contact with each other, and the average distance Dv (ave) was 0 nm. The average distance Dh (ave) between the AlNiAu alloy parts was 2724 nm.

<Example 3>
A first electrode portion was formed in the same manner as in Example 1 except that Ti was 20 nm, Al was 202 nm, Ni was 32 nm, and Au was 60 nm. The film thickness ratio between Al and Ni (Al film thickness / Ni film thickness) is 6.3, and the film thickness ratio between Al and Au (Al film thickness / Au film thickness) is 3.4. The average distance Dv (ave) between the n-AlGaN layer and the AlNi alloy part was 85 nm. The average distance Dh (ave) between the AlNi alloy parts was 560 nm.

<Example 4>
A first electrode portion was formed in the same manner as in Example 1 except that Ti was 21 nm, Al was 177 nm, Ni was 34 nm, and Au was 52 nm. The film thickness ratio between Al and Ni (Al film thickness / Ni film thickness) is 5.3, and the film thickness ratio between Al and Au (Al film thickness / Au film thickness) is 3.4. The average distance Dv (ave) between the n-AlGaN layer and the AlNi alloy part was 150 nm. The average distance Dh (ave) between the AlNi alloy parts was 340 nm.

<Example 5>
A first electrode portion was formed in the same manner as in Example 1 except that Ti was 20 nm, Al was 170 nm, Ni was 35 nm, and Au was 59 nm. The film thickness ratio between Al and Ni (Al film thickness / Ni film thickness) is 4.8, and the film thickness ratio between Al and Au (Al film thickness / Au film thickness) is 3.5. The average distance Dv (ave) between the n-AlGaN layer and the AlNi alloy part was 130 nm. The average distance Dh (ave) between the AlNi alloy parts was 110 nm.

<Example 6>
A first electrode portion was formed in the same manner as in Example 1 except that Ti was 20 nm, Al was 191 nm, Ni was 32 nm, and Au was 58 nm. The film thickness ratio between Al and Ni (Al film thickness / Ni film thickness) is 6.0, and the film thickness ratio between Al and Au (Al film thickness / Au film thickness) is 3.3. The average distance Dv (ave) between the n-AlGaN layer and the AlNi alloy part was 102 nm. The average distance Dh (ave) between the AlNi alloy parts was 337 nm.

<Example 7>
A first electrode portion was formed in the same manner as in Example 1 except that Ti was 20 nm, Al was 212 nm, Ni was 32 nm, and Au was 75 nm. The film thickness ratio between Al and Ni (Al film thickness / Ni film thickness) is 6.7, and the film thickness ratio between Al and Au (Al film thickness / Au film thickness) is 2.8. The average distance Dv (ave) between the n-AlGaN layer and the AlNi alloy part was 55 nm. The average distance Dh (ave) between the AlNi alloy parts was 1009 nm.

<Example 8>
A first electrode portion was formed in the same manner as in Example 1 except that Ti was 20 nm, Al was 210 nm, Ni was 34 nm, and Au was 57 nm. The film thickness ratio between Al and Ni (Al film thickness / Ni film thickness) is 6.3, and the film thickness ratio between Al and Au (Al film thickness / Au film thickness) is 3.7. The average distance Dv (ave) between the n-AlGaN layer and the AlNi alloy part was 42 nm. The average distance Dh (ave) between the AlNi alloy parts was 1900 nm.

<Evaluation>
Next, on the p-GaN layer of each device obtained in Examples 1 to 8 and Reference Examples 1 and 2, Ni was deposited in a thickness of 20 nm and Au in a thickness of 35 nm in this order, and heat treatment was performed at 600 ° C. for 180 seconds. did. As a result, a p-type electrode portion was formed as the second electrode portion on the p-GaN layer of each device, and an ultraviolet light emitting device was obtained from each device.
About each obtained ultraviolet light-emitting device, the contact resistance of the n-AlGaN layer which is an n-type nitride semiconductor layer, and the 1st electrode part was evaluated, respectively. Further, for each of these ultraviolet light emitting devices, the forward voltage Vf, which is an index for reducing the power consumption of the ultraviolet light emitting device, was evaluated.
Specifically, the voltage between the first electrode part and the second electrode part when a constant current of 100 mA was applied to the ultraviolet light emitting device was measured, and the forward voltage Vf was evaluated.

  As described above, for each of the devices obtained in Examples 1 to 8 and Reference Examples 1 and 2, the thickness and ratio of the Ti, Al, Ni, Au layer of the first electrode part, the average distance Dv (ave) of the first electrode part Table 1 summarizes the average interval Dh (ave) and the forward voltage Vf.

  As can be seen from Table 1, it was confirmed that the forward voltage Vf of the ultraviolet light emitting device having an average distance Dv (ave) of 20 nm or more is low. Further, it was confirmed that the forward voltage Vf of the ultraviolet light emitting device having an average interval Dh (ave) of 100 nm to 2500 nm is low. An ultraviolet light emitting device having an average distance Dv (ave) of 20 nm or more or an ultraviolet light emitting device having an average distance Dh (ave) of 100 nm to 2500 nm is realized by forming Al from 160 nm to 270 nm. It is understood. Similarly, it is understood that this can also be realized by setting 5 ≦ Al film thickness / Ni film thickness ≦ 9.4. Similarly, it is understood that this can be realized by setting 2.8 ≦ Al film thickness / Au film thickness ≦ 5.

As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.
The order of execution of each process such as operations, procedures, steps, and stages in the apparatus, system, program, and method shown in the claims, the description, and the drawings is particularly “before” or “prior to”. It should be noted that the output can be realized in any order unless the output of the previous process is used in the subsequent process. Regarding the operation flow in the claims, the description, and the drawings, even if it is described using “first”, “next”, etc. for convenience, it means that it is essential to carry out in this order. It is not a thing.

DESCRIPTION OF SYMBOLS 10 Substrate 20 N-type nitride semiconductor layer 30 1st electrode part 40 Light emitting layer 50 P-type nitride semiconductor layer 100 Ultraviolet light-emitting device

Claims (6)

an n-type nitride semiconductor layer;
A first electrode part that includes Ti, Al, Ni, Au as constituent elements, has an AlNi alloy part, and is provided on the n-type nitride semiconductor layer;
a p-type nitride semiconductor layer;
A light emitting layer located between the n-type nitride semiconductor layer and the p-type nitride semiconductor layer;
With
The ultraviolet light emitting device in which an average distance between the n-type nitride semiconductor layer and the AlNi alloy part is 20 nm or more when a portion including the AlNi alloy part of the first electrode part is viewed in cross section. an n-type nitride semiconductor layer;
A first electrode part that includes Ti, Al, Ni, Au as constituent elements, has an AlNi alloy part, and is provided on the n-type nitride semiconductor layer;
a p-type nitride semiconductor layer;
A light emitting layer provided between the n-type nitride semiconductor layer and the p-type nitride semiconductor layer;
With
The ultraviolet light emitting device in which an average interval between the AlNi alloy parts is 100 nm or more and 2500 nm or less when the portion including the AlNi alloy part of the first electrode part is viewed in cross section. The n-type nitride of a semiconductor wafer comprising an n-type nitride semiconductor layer, a p-type nitride semiconductor layer, and a light emitting layer located between the n-type nitride semiconductor layer and the p-type nitride semiconductor layer Ti is formed to a thickness of 5 nm to 40 nm on the semiconductor layer, Al is formed to a thickness of 160 nm to 270 nm on the Ti, and Ni is formed to a thickness of 5 nm to 50 nm on the Al. A deposition step of forming Au on the Ni to a thickness of 40 nm to 100 nm;
An ultraviolet light emitting device manufacturing method comprising: an annealing step for heat treatment after the deposition step. The n-type nitride of a semiconductor wafer comprising an n-type nitride semiconductor layer, a p-type nitride semiconductor layer, and a light emitting layer located between the n-type nitride semiconductor layer and the p-type nitride semiconductor layer Ti is formed to a thickness of 5 nm to 40 nm on the semiconductor layer, Al is formed on the Ti, Ni is formed on the Al, and Au is formed to a thickness of 40 nm to 100 nm on the Ni. A deposition process to form;
An annealing step for heat treatment after the deposition step,
In the deposition step, the Al and Ni are formed so that the film thickness ratio of Al to Ni (Al film thickness / Ni film thickness) satisfies 5 or more and 9.4 or less, respectively. Method. The n-type nitride of a semiconductor wafer comprising an n-type nitride semiconductor layer, a p-type nitride semiconductor layer, and a light emitting layer located between the n-type nitride semiconductor layer and the p-type nitride semiconductor layer On the semiconductor layer, Ti is formed to a thickness of 5 nm to 40 nm, Al is formed on the Ti, Ni is formed on the Al to a thickness of 5 nm to 50 nm, and Au is formed on the Ni. A deposition process to form;
An annealing step for heat treatment after the deposition step,
In the deposition step, the Al and Au are respectively formed so that the film thickness ratio of Al to Au (Al film thickness / Au film thickness) satisfies 2.8 or more and 5 or less. Method.   An apparatus comprising the ultraviolet light emitting device according to claim 1.