JP4252622B1 - Manufacturing method of semiconductor light emitting device - Google Patents

Abstract

A semiconductor light emitting device capable of efficiently outputting ultraviolet light and a method for manufacturing the same are provided.
A translucent electrode including a p-type semiconductor layer, a semiconductor layer having an emission wavelength in at least an ultraviolet region, and a translucent electrode provided on the p-type semiconductor layer. Is a semiconductor light emitting device 1 including a crystallized IZO film.
[Selection] Figure 1

Description

  The present invention relates to a semiconductor light emitting device, a semiconductor light emitting device, and a lamp using the semiconductor light emitting device, and more particularly, to a semiconductor light emitting device excellent in ultraviolet light emission output (Po), a method for manufacturing the semiconductor light emitting device, and a lamp using the same. .

  In recent years, gallium nitride compound semiconductor light emitting devices have attracted attention as short wavelength light emitting devices. Gallium nitride-based compound semiconductor light-emitting devices are formed on a substrate made of various oxides and III-V compounds such as sapphire single crystals, metal organic chemical vapor deposition (MOCVD), and molecular beam epitaxy (MBE). ) Or the like to form a gallium nitride compound semiconductor.

  In such a gallium nitride-based compound semiconductor light emitting device, since current diffusion in the lateral direction is small, current is injected only into the semiconductor directly under the electrode, and light emitted from the light emitting layer is blocked by the electrode and taken out to the outside. There is an inconvenience that it is not. In order to solve this inconvenience, a transparent electrode is usually used as the positive electrode of the gallium nitride compound semiconductor light emitting device, and light is extracted through the positive electrode.

As the transparent electrode, a known transparent conductive material such as Ni / Au or ITO is used.
In recent years, an oxide-based material mainly composed of In ₂ O ₃ , ZnO, or the like that is excellent in translucency has been generally used as a transparent electrode. ITO (indium tin oxide), which is most utilized as a material for transparent electrodes, has a low specific resistance of about 2 × 10 ⁻⁴ Ωcm by doping In ₂ O ₃ with 5 to 20% by mass of SnO ₂ . A transparent conductive film can be obtained.

Since the ITO film has a band gap of 3 eV or more, it exhibits high transmittance for light having a wavelength region in the visible light region (> 90%). However, in the ITO film, the amount of light absorbed in the film from the wavelength region of about 400 nm or less increases, and thus the transmittance decreases sharply in the wavelength region of 400 nm or less. Therefore, when an ITO film is used as an electrode of a light emitting element that emits light having a wavelength in the ultraviolet region, there has been a problem that the light emission output is lowered.
In order to solve this problem, a light-emitting element having a structure that prevents ultraviolet rays from being absorbed by the transparent electrode and converts the ultraviolet rays into visible light before reaching the transparent electrode has been proposed (for example, see Patent Document 1). ing.

Moreover, in order to reduce the light absorbency of a translucent electrode, the flip-chip type light emitting element (For example, refer patent document 2) provided with the through-hole for light emission, and the adhesive metal layer with a high light reflectance. Proposed.
JP-A-5-299175 JP 2005-123501 A

However, in Patent Document 1, ultraviolet light is converted to visible light before the light reaches the transparent electrode, so that a sufficient light output of ultraviolet light cannot be obtained.
Further, even when the technique described in Patent Document 2 is used, since the translucent electrode is made of an ITO film, light having a wavelength in the ultraviolet region is absorbed by the ITO film. A sufficient light output was not obtained.

The present invention has been made in view of the above circumstances, and an object of the present invention is to solve the above-described problems and provide a semiconductor light-emitting device capable of efficiently outputting ultraviolet light and a method for manufacturing the same.
It is another object of the present invention to provide a lamp having excellent characteristics using a semiconductor light emitting element that can output ultraviolet light efficiently.

As a result of intensive studies to solve the above problems, the present inventor has completed the present invention.
That is, the present invention relates to the following.
(1) A method for manufacturing a semiconductor light-emitting device, comprising: a p-type gallium nitride compound semiconductor layer; and a translucent electrode including an IZO film provided on the p-type gallium nitride compound semiconductor layer. A step of forming an amorphous IZO film on the type gallium nitride-based compound semiconductor layer and an annealing treatment at 500 ° C. to 900 ° C., the amorphous IZO film is formed from In ₂ O ₃ by X-ray diffraction. And an annealing step for forming an IZO film from which a peak is detected.

(2) The method for manufacturing a semiconductor light-emitting element according to (1), comprising a step of patterning the amorphous IZO film by using a photolithography method and wet etching before the annealing step. .
(3) The method for manufacturing a semiconductor light-emitting element according to (1) or (2), wherein the annealing treatment is performed in an atmosphere not containing O ₂ .
(4) The semiconductor light emitting element according to any one of (1) to (3), wherein the annealing treatment is performed in an N ₂ atmosphere or a mixed gas atmosphere of N ₂ and H ₂ . Production method.
(5) The method for manufacturing a semiconductor light-emitting element according to any one of (1) to (4), wherein the ZnO concentration in the IZO film is in the range of 5 to 15% by mass.

Since the semiconductor light emitting device of the present invention includes an IZO (indium zinc oxide) film in which the translucent electrode is crystallized, the translucent electrode has a high transmissivity for light in the ultraviolet region. Become. More specifically, the crystallized IZO film is superior to the ITO film in light transmittance having a wavelength region in the vicinity of 400 nm that is an ultraviolet region. Therefore, the semiconductor light emitting device of the present invention has a small amount of light in the ultraviolet region absorbed by the translucent electrode, can output ultraviolet light efficiently, and has high ultraviolet light emission output.
In addition, according to the method for manufacturing a semiconductor light emitting device of the present invention, after forming an amorphous IZO film on the p-type semiconductor layer, annealing is performed at 500 ° C. to 900 ° C., thereby crystallizing the IZO film. It is possible to realize a semiconductor light-emitting element that includes a translucent electrode that contains UV light and that can efficiently output ultraviolet light.
In addition, by forming a lamp using the semiconductor light emitting device of the present invention, a lamp having excellent light emission characteristics that can efficiently output ultraviolet light can be obtained.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of a semiconductor light emitting device, a method for manufacturing a semiconductor light emitting device, and a lamp using the semiconductor light emitting device of the present invention will be described with reference to the drawings as appropriate.
FIG. 1 is a cross-sectional view schematically showing an example of the semiconductor light emitting device of the present invention, and FIG. 2 is a plan view schematically showing the semiconductor light emitting device shown in FIG.
A semiconductor light emitting device 1 shown in FIG. 1 is a face-up type, and an n-type GaN layer (n-type semiconductor layer) constituting a gallium nitride-based compound semiconductor layer having a light emission wavelength at least in the ultraviolet region on a substrate 11. 12, a light emitting layer 13, and a p-type GaN layer (p-type semiconductor layer) 14, and a positive electrode 15 made of a crystallized IZO film on the p-type GaN layer 14 of the gallium nitride-based compound semiconductor layer ( A translucent electrode) is laminated and is generally configured. A positive electrode bonding pad 16 is formed on a part of the positive electrode 15. A negative electrode 17 of a bonding pad is formed in the negative electrode formation region on the n-type GaN layer 12.

Below, each structure of the semiconductor light-emitting device of this invention is explained in full detail.
"substrate"
As the substrate 11, sapphire single crystal (Al ₂ O ₃ ; A plane, C plane, M plane, R plane), spinel single crystal (MgAl ₂ O ₄ ), ZnO single crystal, LiAlO ₂ single crystal, LiGaO ₂ single crystal. Known substrate materials such as oxide single crystals such as MgO single crystals, Si single crystals, SiC single crystals, GaAs single crystals, AlN single crystals, GaN single crystals, and boride single crystals such as ZrB ₂ are used without any limitation. be able to.
The plane orientation of the substrate is not particularly limited. The substrate 11 may be a just substrate or a substrate with an off angle.

"Gallium nitride compound semiconductor layer"
As the n-type GaN layer 12, the light emitting layer 13, and the p-type GaN layer (p-type semiconductor layer) 14, those having various structures are well known, and these well-known materials can be used without any limitation. In particular, the p-type semiconductor layer may be a p-type GaN layer having a relatively low carrier concentration, for example, a p-type GaN layer having a relatively low carrier concentration, for example, about 1 × 10 ¹⁷ cm ^−3. The positive electrode 15 of the crystallized IZO film constituting the present invention can be applied.

Examples of the gallium nitride-based compound semiconductor include semiconductors having various compositions represented by the general formula Al _x In _y Ga _1-xy N (0 ≦ x <1, 0 ≦ y <1, 0 ≦ x + y <1). As a well-known gallium nitride compound semiconductor constituting the n-type GaN layer, the light emitting layer, and the p-type GaN layer in the present invention, the general formula Al _x In _y Ga _1-xy N (0 ≦ x <1, Semiconductors having various compositions represented by 0 ≦ y <1, 0 ≦ x + y <1) can be used without any limitation.

The growth method of these gallium nitride-based compound semiconductors is not particularly limited, and group III nitride semiconductors such as MOCVD (metal organic chemical vapor deposition), HVPE (hydride vapor deposition), MBE (molecular beam epitaxy), etc. All methods known to grow can be applied. A preferred growth method is the MOCVD method from the viewpoint of film thickness controllability and mass productivity.
In the MOCVD method, hydrogen (H ₂ ) or nitrogen (N ₂ ) as a carrier gas, trimethyl gallium (TMG) or triethyl gallium (TEG) as a Ga source which is a group III source, trimethyl aluminum (TMA) or triethyl aluminum as an Al source (TEA), trimethylindium (TMI) or triethylindium (TEI) as the In source, ammonia (NH ₃ ), hydrazine (N ₂ H ₄ ), or the like as the N source which is a group V material. In addition, as a dopant, monosilane (SiH ₄ ) or disilane (Si ₂ H ₆ ) is used as a Si raw material for n-type, germane gas (GeH ₄ ) is used as a Ge raw material, and Mg raw material is used for a p-type. For example, biscyclopentadienyl magnesium (Cp ₂ Mg) or bisethylcyclopentadienyl magnesium ((EtCp) ₂ Mg) is used.

  As an example of such a gallium nitride compound semiconductor layer made of a gallium nitride compound semiconductor, a gallium nitride compound semiconductor layer 20 having a stacked structure as shown in FIG. 3 can be cited. In the gallium nitride compound semiconductor layer 20 shown in FIG. 3, a buffer layer (not shown) made of AlN is laminated on a substrate 21 made of sapphire, and a GaN foundation layer (n-type semiconductor layer) 22 and n-type GaN are sequentially formed. Contact layer (n-type semiconductor layer) 23, n-type AlGaN cladding layer (n-type semiconductor layer) 24, light-emitting layer 25 made of InGaN, p-type AlGaN cladding layer 26 (p-type semiconductor layer), p-type GaN contact layer (p Type semiconductor layer) 27 is laminated.

"Positive electrode (IZO film)"
As shown in FIG. 1, an IZO film crystallized as the positive electrode 15 is formed on the p-type GaN layer 14. The IZO film is formed directly on the p-type GaN layer 14 or on the p-type GaN layer 14 via a metal layer or the like. When a metal layer is sandwiched between the positive electrode 15 and the p-type GaN layer 14, the drive voltage (Vf) of the semiconductor light emitting device 1 can be reduced, but the transmittance is reduced and the output is lowered. End up. Therefore, the driving voltage (Vf) and the output are balanced according to the use of the semiconductor light emitting element 1 and so on, and it is appropriately determined whether or not a metal layer is sandwiched between the positive electrode 15 and the p-type GaN layer 14. Here, it is preferable to use a metal layer made of Ni, Ni oxide, Pt, Pd, Ru, Rh, Re, Os, or the like.

Further, it is preferable to use a composition having the lowest specific resistance as the IZO film. For example, the ZnO concentration in the IZO film is preferably in the range of 5 to 15% by mass, and more preferably 10% by mass.
The thickness of the IZO film is preferably in the range of 35 nm to 10000 nm (10 μm), more preferably in the range of 100 nm to 1 μm, in order to achieve low resistivity and high transmittance. Furthermore, from the viewpoint of production cost, the thickness of the IZO film is preferably 1000 nm (1 μm) or less.

Next, an example of a method for forming the IZO film will be described.
First, an amorphous IZO film is formed over the entire area on the p-type GaN layer 14. As a method for forming the IZO film, any known method used for forming a thin film may be used as long as it can form an amorphous IZO film. For example, a film can be formed using a method such as a sputtering method or a vacuum vapor deposition method, but it is more preferable to use a sputtering method in which particles and dust generated at the time of film formation are small compared to the vacuum vapor deposition method. In the case of using the sputtering method, the In ₂ O ₃ target and the ZnO target can be formed by revolving film formation by the RF magnetron sputtering method. To increase the film formation rate, IZO The target may be formed by a DC magnetron sputtering method. In order to reduce damage to the p-type GaN layer 14 due to plasma, the discharge output of sputtering is preferably 1000 W or less.

The amorphous IZO film formed in this way is patterned by using a well-known photolithography method and etching in a region excluding the positive electrode forming region which is a region for forming the positive electrode 15 on the p-type GaN layer 14. Then, as shown in FIG. 2, it is formed only in the positive electrode forming region.
It is desirable that the patterning of the IZO film be performed before the annealing process described later. Since the amorphous IZO film is converted into a crystallized IZO film by the annealing process, etching becomes difficult as compared with the amorphous IZO film. On the other hand, since the IZO film before the annealing step is in an amorphous state, it can be easily and accurately etched using a known etching solution. Further, the etching of the IZO film may be performed using a dry etching apparatus.

  In this embodiment, after patterning the IZO film, an annealing process is performed at 500 ° C. to 900 ° C. to turn the amorphous IZO film into a crystallized IZO film (annealing step). By using a crystallized IZO film, the transmittance of light having a wavelength in the ultraviolet region (350 nm to 420 nm) can be improved. Although the mechanism of increasing the transmittance in the ultraviolet region by using a crystallized IZO film is not clear, it is considered that the band gap of the IZO film is increased by crystallizing.

Further, the annealing treatment of the IZO film is preferably performed in an atmosphere not containing O _2, and the atmosphere not containing O ₂ includes an inert gas atmosphere such as an N ₂ atmosphere or an inert gas such as N _2. And a mixed gas atmosphere of H ₂ , and an N ₂ atmosphere or a mixed gas atmosphere of N ₂ and H ₂ is desirable. When the annealing treatment of the IZO film is performed in an N ₂ atmosphere or a mixed gas atmosphere of N ₂ and H ₂ , the IZO film can be crystallized and the sheet resistance of the IZO film can be effectively reduced. . In particular, when it is desired to reduce the sheet resistance of the IZO film, the IZO film may be annealed in a mixed gas atmosphere of N ₂ and H ₂ . The ratio of N ₂ and H ₂ in the mixed gas atmosphere is preferably 100: 1 to 1: 100.

On the other hand, for example, when the annealing process is performed in an atmosphere containing O ₂ , the sheet resistance of the IZO film increases. When annealing is performed in an atmosphere containing O ₂ , the sheet resistance of the IZO film is considered to increase because oxygen vacancies in the IZO film decrease. The reason why the IZO film is conductive is that oxygen vacancies are present in the IZO film, thereby generating electrons serving as carriers. Therefore, it is considered that the oxygen vacancies, which are generation sources of carrier electrons, are reduced by annealing in an atmosphere containing O ₂ , the carrier concentration of the IZO film is reduced, and the sheet resistance is increased.

  The annealing temperature of the IZO film is set to 500 ° C. to 900 ° C. When annealing is performed at a temperature lower than 500 ° C., the IZO film may not be sufficiently crystallized, and the transmittance of the IZO film in the ultraviolet region may not be sufficiently high. In addition, when the annealing process is performed at a temperature exceeding 900 ° C., the semiconductor layer under the IZO film may be deteriorated.

In this embodiment, annealing is used to crystallize the IZO film. However, in the semiconductor light emitting device of the present invention, any method can be used as long as the IZO film can be crystallized. Alternatively, a method using an RTA annealing furnace, a method of performing laser annealing, a method of performing electron beam irradiation, or the like may be used.
Further, the positive electrode 15 made of the crystallized IZO film is not only effective in improving the light extraction efficiency of a semiconductor light emitting device having a central wavelength in the ultraviolet region (350 nm to 420 nm). Even in the case of a semiconductor light emitting element having a blue region of about 450 nm, the light extraction efficiency can be improved if the light emitting region is provided at 350 nm to 420 nm.

  In addition, since the IZO film crystallized by annealing treatment has better adhesion to the p-type GaN layer 14 and the positive electrode bonding pad 16 than the amorphous IZO film, the IZO film is less susceptible to peeling due to peeling in the manufacturing process of the semiconductor light emitting device. The rate can be prevented from decreasing. In addition, a crystallized IZO film is preferable because it has little reaction with moisture in the air, and therefore has little deterioration in characteristics in a long-term durability test.

"Negative electrode"
The negative electrode 17 is exposed to the n-type GaN layer 12 exposed by etching away a part of the p-type GaN layer 14, the light emitting layer 13, and the n-type GaN layer 12 as shown in FIG. Provided on top. As the negative electrode 17, for example, various compositions and structures such as those made of Ti / Au are well known, and these known negative electrodes can be used without any limitation.

"Positive electrode bonding pad"
A positive electrode bonding pad 16 for electrical connection with a circuit board or a lead frame is provided on a part of the IZO film layer which is the positive electrode 15. Various structures using materials such as Au, Al, Ni, and Cu are well known for the positive electrode bonding pad 16, and those known materials and structures can be used without any limitation. Further, the thickness of the positive electrode bonding pad 16 is preferably in the range of 100 to 1000 nm. Further, in view of the characteristics of the bonding pad, the larger the thickness, the higher the bondability. Therefore, the thickness of the positive electrode bonding pad 16 is more preferably 300 nm or more. Furthermore, it is preferable to set it as 500 nm or less from a viewpoint of manufacturing cost.

"Protective layer"
In order to prevent oxidation of the IZO film, it is further preferable to form a protective layer (not shown) so as to cover the entire region on the IZO film except the region where the positive electrode bonding pad 16 is formed. This protective layer is preferably made of a material having excellent light-transmitting properties, and is preferably formed of an insulating material in order to prevent leakage between the p-type semiconductor layer and the n-type semiconductor layer. As a material constituting the protective layer, for example, it is desirable to use SiO ₂ , Al ₂ O ₃ or the like. Moreover, the film thickness of a protective layer should just be a film thickness which can prevent the oxidation of an IZO film | membrane and is excellent in translucency, for example, the film thickness of 20 nm-500 nm is good.

[lamp]
As described above, the semiconductor light emitting device of the present invention described above can be configured as a lamp by providing a transparent cover by means well known to those skilled in the art. Moreover, a white lamp can also be comprised by combining the semiconductor light-emitting device of this invention and the cover which has fluorescent substance.
Moreover, the semiconductor light emitting device of the present invention can be configured as an LED lamp without any limitation using a conventionally known method. The lamp can be used for any purpose such as a bullet type for general use, a side view type for portable backlight use, and a top view type used for a display.

  FIG. 4 is a schematic configuration diagram for explaining an example of the lamp of the present invention. The lamp 30 shown in FIG. 4 is obtained by mounting a face-up type semiconductor light emitting device of the present invention in a bullet shape. In the lamp 30 shown in FIG. 4, the semiconductor light emitting device 1 shown in FIG. 1 is bonded to one of the two frames 31 and 32 with a resin or the like, and the positive electrode bonding pad 16 and the negative electrode 17 are made of a wire 33 made of a material such as gold. , 34 are joined to the frames 31, 32, respectively. Further, as shown in FIG. 4, a mold 35 made of a transparent resin is formed around the semiconductor light emitting element 1.

  In addition, this invention is not limited to embodiment mentioned above. For example, the semiconductor layer provided in the semiconductor light emitting device of the present invention is not limited to the above-described gallium nitride compound semiconductor layer, and any light emitting device having a light emission wavelength in at least the ultraviolet region can be used. Good.

(Experiment 1) “Atmosphere in annealing treatment of IZO film”
The relationship between the atmosphere in the annealing process of the IZO film and the sheet resistance of the IZO film after the annealing process was examined as follows.
That is, on a glass substrate to form an IZO film in an amorphous state (250 nm), at each temperature of 300 ° C. to 600 ° C. The resulting IZO film, and when annealed in _{an N 2} atmosphere, in _{N 2} O The sheet resistance when annealed in a mixed gas atmosphere containing 25% of ₂ was measured. The results are shown in Table 1.

From Table 1, it can be seen that when the annealing treatment is performed in a mixed gas atmosphere containing O _{2 in} N ₂ , the sheet resistance increases as the annealing temperature increases. In contrast, when annealing is performed in an N ₂ atmosphere not containing O ₂ , the sheet resistance decreases as the annealing temperature increases. The sheet resistance of the 250 nm thick IZO film in an amorphous state before annealing was 15 Ω / sq.

(Experimental example 2) “IZO film annealing temperature”
The relationship between the annealing temperature of the IZO film and the crystallization of the IZO film was examined as follows.
That is, an amorphous IZO film (250 nm) was formed on a glass substrate, and the obtained IZO film without annealing was measured by an X-ray diffraction (XRD) method. In addition, an amorphous IZO film formed on a glass substrate is annealed at 300 ° C. to 800 ° C. for 1 minute in an N ₂ atmosphere, and the annealed IZO film is subjected to an X-ray diffraction (XRD) method. Measured with The result is shown in FIG.

FIG. 5 is a graph showing the results of X-ray diffraction (XRD) of the IZO film, the horizontal axis indicates the diffraction angle (2θ (°)), and the vertical axis indicates the analysis intensity (s).
As shown in FIG. 5, when the IZO film is annealed at an annealing temperature of 600 ° C. or higher, the X-ray peak composed of In ₂ O ₃ is mainly detected and it can be seen that it is crystallized. . It can also be seen that when the IZO film is annealed at an annealing temperature of 400 ° C. or lower, it is not crystallized.

(Experimental example 3) "Transmission rate of IZO film"
The relationship between the annealing temperature of the IZO film and the transmittance of the IZO film after the annealing was examined as follows.
That is, the transmittance of the IZO film without annealing treatment obtained in Experimental Example 2 and the IZO film after annealing treatment at 300 ° C. and 600 ° C. were measured. The result is shown in FIG.
Note that an ultraviolet-visible spectrophotometer UV-2450 manufactured by Shimadzu Corporation was used for measuring the transmittance of the IZO film. Further, the transmittance value was calculated by subtracting the light transmission blank value obtained by measuring the transmittance of only the glass substrate.

FIG. 6 is a graph showing the transmittance of the IZO film, where the horizontal axis indicates the wavelength (nm) and the vertical axis indicates the transmittance (%).
FIG. 6 shows that when the IZO film is annealed at an annealing temperature of 600 ° C., the transmittance in the ultraviolet region (350 nm to 420 nm) is 20 to 30% higher than that of the IZO film without annealing. I understand.

[Example 1] (Production of gallium nitride compound semiconductor layer)
The gallium nitride compound semiconductor layer 20 shown in FIG. 3 was manufactured as follows. That is, an undoped GaN underlayer (layer thickness = 2 μm) 22 and Si-doped n-type are formed on a substrate 21 made of sapphire c-plane ((0001) crystal plane) via a buffer layer (not shown) made of AlN. GaN contact layer (layer thickness = 2 μm, carrier concentration = 1 × 10 ¹⁹ cm ⁻³ ) 23, Si-doped n-type Al _0.07 Ga _0.93 N cladding layer (layer thickness = 12.5 nm, carrier concentration = 1 × 10 ¹⁸ cm ⁻³ ) 24, 6 Si-doped GaN barrier layers (layer thickness = 14.0 nm, carrier concentration = 1 × 10 ¹⁸ cm ⁻³ ) and 5 layers of undoped In _0.20 Ga _0.80 N Light emitting layer 25 having a multiple quantum structure composed of a well layer (layer thickness = 2.5 nm), Mg-doped p-type Al _0.07 Ga _0.93 N cladding layer (layer thickness 10 nm) 26, and Mg-doped p-type GaN A contact layer (layer thickness = 100 nm) 27 was sequentially laminated. The constituent layers 22 to 27 of the laminated structure of the gallium nitride compound semiconductor layer 20 were grown by a low pressure MOCVD means.

(Manufacture of semiconductor light emitting devices)
Next, using the obtained gallium nitride compound semiconductor layer 20 shown in FIG. 3, a gallium nitride compound semiconductor light emitting device was fabricated. First, the surface of the p-type GaN contact layer 27 of the gallium nitride compound semiconductor layer 20 is cleaned using HF and HCl, and an IZO film having a thickness of 220 nm is formed on the p-type GaN contact layer 27 by DC magnetron sputtering. A film was formed.
For sputtering of the IZO film, an IZO target having a ZnO concentration of 10% by mass was used. The IZO film was formed at a pressure of about 0.3 Pa by introducing Ar gas at 70 sccm.

  The IZO film formed by the above method had a transmittance of about 60% in the wavelength region near 400 nm, and the sheet resistance was 17Ω / sq. Moreover, it was confirmed that the IZO film immediately after film formation formed by the above-described method is amorphous by measuring by an X-ray diffraction (XRD) method.

Thereafter, the amorphous IZO film was patterned by using a photolithography method and wet etching, so that the IZO film was formed only in the positive electrode formation region on the p-type GaN contact layer 27. The amorphous IZO film was etched at an etching rate of about 40 nm / min.
After patterning the IZO film, annealing was performed at 600 ° C. for 1 min in an N ₂ gas atmosphere using an RTA annealing furnace.

The annealed IZO film had high translucency in the wavelength region near 400 nm, and the transmittance in the wavelength region of 400 nm was 90% or more. The sheet resistance of the IZO film was 14Ω / sq. Further, in the XRD measurement after the annealing treatment, an X-ray peak composed of In ₂ O ₃ was mainly detected, and it was confirmed that the IZO film was crystallized.

Next, dry etching was performed on the region where the n-type electrode was to be formed, and the surface of the Si-doped n-type GaN contact layer 23 was exposed only in that region. Thereafter, a first layer made of Cr (layer thickness = 40 nm) and a second layer made of Ti are formed on a part of the IZO film layer (positive electrode) and the Si-doped n-type GaN contact layer 23 by vacuum deposition. A layer (layer thickness = 100 nm) and a third layer (layer thickness = 400 nm) made of Au were sequentially stacked to form a positive electrode bonding pad and a negative electrode, respectively. After forming the positive electrode bonding pad and the negative electrode, the back surface of the substrate 11 made of sapphire was polished using abrasive grains such as diamond fine grains and finally finished to a mirror surface.
Thereafter, the laminated structure was cut and separated into 350 μm square individual chips to obtain a semiconductor light emitting device.

(Measurement of drive voltage (Vf) and light emission output (Po))
The semiconductor light emitting device (chip) thus obtained was placed on a lead frame and connected to the lead frame with a gold (Au) wire. The forward voltage (drive voltage: Vf) at a current application value of 20 mA of the semiconductor light emitting element was measured by energization with the probe needle. Moreover, the light emission output (Po) and the light emission wavelength were measured with a general integrating sphere.
It was confirmed that the light emission distribution on the light emitting surface emitted light on the entire surface of the positive electrode. Further, the semiconductor light emitting device had an emission wavelength in a wavelength region near 400 nm, Vf was 3.3 V, and Po was 15 mW.

[Example 2]
A semiconductor light emitting device was fabricated in the same manner as in Example 1 except that a mixed gas of N ₂ and H ₂ was used as the annealing gas. The IZO film immediately after annealing had a transmittance of 90% or more and a sheet resistance of 11Ω / sq in the wavelength region near 400 nm. Further, the obtained semiconductor light emitting device had an emission wavelength in a wavelength region near 400 nm, Vf was 3.25 V, and Po was 15 mW.

[Comparative Example 1]
A semiconductor light emitting device was fabricated in the same manner as in Example 1 except that the annealing temperature was 300 ° C. The annealed IZO film had a transmittance of about 70% in the wavelength region near 400 nm and a sheet resistance of 16Ω / sq. Further, the obtained semiconductor light emitting device had an emission wavelength in a wavelength region near 400 nm, Vf was 3.3 V, and Po was 12 mW.

[Comparative Example 2]
Similar to Example 1, an ITO film of 250 nm was formed on the p-type GaN contact layer 27 of the gallium nitride-based compound semiconductor layer 20 by a sputtering method. Thereafter, the amorphous IZO film was wet-etched using a mixed solution of FeCl ₃ and HCl, so that the IZO film was formed only in the positive electrode formation region on the p-type GaN contact layer 27. After patterning the IZO film, two annealing processes were performed: an annealing process at 600 ° C. for 1 min in an N ₂ gas atmosphere containing 25% O ₂ and an annealing process at 500 ° C. for 1 min in an N ₂ atmosphere. The two annealed ITO films had a transmittance of about 80% in the wavelength region near 400 nm and a sheet resistance of 15Ω / sq.
Further, after two annealing treatments, a semiconductor light emitting device was produced in the same manner as in Example 1. The obtained semiconductor light emitting device had an emission wavelength in a wavelength region near 400 nm, Vf was 3.3 V, and Po was 13 mW.

From the results of Examples and Examples 2 and Comparative Examples 1 and 2, the semiconductor light emitting devices of Examples and Example 2 constitute a positive electrode as compared with the semiconductor light emitting devices of Comparative Examples 1 and 2. It became clear that the transmittance of the IZO film after annealing was high and the sheet resistance was low.
Further, it was revealed that the semiconductor light emitting devices of Examples and Example 2 were superior in light emission output (Po) of light in the ultraviolet region as compared with the semiconductor light emitting devices of Comparative Examples 1 and 2. .

FIG. 1 is a cross-sectional view schematically showing an example of the semiconductor light emitting device of the present invention. FIG. 2 is a plan view schematically showing the semiconductor light emitting device shown in FIG. FIG. 3 is a cross-sectional view schematically showing an example of a gallium nitride compound semiconductor layer. FIG. 4 is a cross-sectional view schematically illustrating a lamp configured using the semiconductor light emitting device of the present invention. FIG. 5 is a graph showing an X-ray diffraction (XRD) result of the IZO film. FIG. 6 is a graph showing the transmittance of the IZO film.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Semiconductor light-emitting device 11, 21 ... Substrate, 12 ... n-type GaN layer (n-type semiconductor layer), 13 ... Light-emitting layer, 14 ... p-type GaN layer (p-type semiconductor layer), 15 ... Positive electrode (translucent) Electrode), 16 ... positive electrode bonding pad, 17 ... negative electrode, 20 ... gallium nitride compound semiconductor layer, 22 ... GaN underlayer (n-type semiconductor layer), 23 ... n-type GaN contact layer (n-type semiconductor layer), 24 ... n-type AlGaN cladding layer (n-type semiconductor layer), 25... light emitting layer, 26... p-type AlGaN cladding layer (p-type semiconductor layer), 27... p-type GaN contact layer (p-type semiconductor layer), 30.

Claims (5)

A method of manufacturing a semiconductor light emitting device comprising a p-type gallium nitride compound semiconductor layer and a translucent electrode including an IZO film provided on the p-type gallium nitride compound semiconductor layer,
Forming an amorphous IZO film on the p-type gallium nitride compound semiconductor layer;
An annealing step of performing an annealing process at 500 ° C. to 900 ° C. to convert the amorphous IZO film into an IZO film in which a peak composed of In ₂ O ₃ is detected by X-ray diffraction. A method for manufacturing a semiconductor light emitting device.   2. The method of manufacturing a semiconductor light emitting element according to claim 1, further comprising a step of patterning the amorphous IZO film by using a photolithography method and wet etching before the annealing step. The method for manufacturing a semiconductor light emitting element according to claim 1, wherein the annealing treatment is performed in an atmosphere not containing O ₂ . 4. The method of manufacturing a semiconductor light emitting element according to claim 1, wherein the annealing treatment is performed in an N ₂ atmosphere or a mixed gas atmosphere of N ₂ and H ₂ .   5. The method for manufacturing a semiconductor light-emitting element according to claim 1, wherein a ZnO concentration in the IZO film is in a range of 5 to 15 mass%.

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