JP2008283096A - Semiconductor light-emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor light-emitting element enabling high luminance and low forward voltage. <P>SOLUTION: The semiconductor light-emitting element has: a reflection metal film (10) having a reflecting layer formed on a second main surface side of a group III-V compound semiconductor layer (11), where a first main surface side of the group III-V compound semiconductor layer (11), having a light-emitting layer (5) is used as a light-extracting surface (11a); a conductive support substrate (20) coupled via the reflection metal film (10); and an ohmic contact bonding portion (9), disposed so as to be dispersed on an interface between the group III-V compound semiconductor layer (11) and the reflecting metal layer (10). The ohmic contact bonding portion (9) has an ohmic contact metal layer (9a) bonded by ohmic contact to the group III-V compound semiconductor layer (11); and an oxidation-preventing metal layer (9b), formed to contact to the reflecting metal film (10) and containing 90% or higher metal having ionization tendency that is smaller than that of pure silver. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor light emitting element including a reflective metal film that reflects light from a light emitting layer to a light extraction surface side.

  Conventionally, light-emitting diodes (LEDs), which are semiconductor light-emitting elements, have recently been able to grow GaN-based and AlGaInP-based high-quality crystals by the MOVPE method. Therefore, high brightness of blue, green, orange, yellow, and red LED can be manufactured. And with the increase in the brightness of LEDs, its application has spread to brake lamps for automobiles, backlights for liquid crystal displays, and the like, and the demand is increasing year by year.

  Currently, since high-quality crystals can be grown by the MOVPE method, the internal efficiency of the light-emitting element is approaching the theoretical limit value. However, the light extraction efficiency from the light emitting element is still low, and it is important to improve the light extraction efficiency. For example, a high-intensity red LED is formed of an AlGaInP-based material, and an n-type AlGaInP layer and a p-type AlGaInP layer made of an AlGaInP-based material having a lattice-matched composition on a conductive GaAs substrate, and an AlGaInP sandwiched between them. A double heterostructure having a light emitting layer (active layer) made of GaInP is formed. However, since the band gap of the GaAs substrate is narrower than the band gap of the light emitting layer, most of the light from the light emitting layer is absorbed by the GaAs substrate, and the light extraction efficiency is significantly reduced.

  There is also a method for improving light extraction efficiency by reducing the absorption of light in the GaAs substrate by forming a multilayer reflective film structure composed of semiconductor layers having different refractive indexes between the light emitting layer and the GaAs substrate. However, this method can reflect only light having a narrow incident angle limited to the multilayer reflective film structure.

Therefore, a double heterostructure made of an AlGaInP-based material is attached to a Si support substrate having a thermal conductivity higher than that of the GaAs substrate through a highly reflective metal film, and then the GaAs substrate used for growth is removed. A method has been proposed (see, for example, Patent Document 1). When this method is used, since a metal film is used as the reflection film, high reflection is possible regardless of the angle of incidence of light on the metal film.
In addition, metals such as gold, aluminum, and silver that have high reflectivity as the reflective film cannot be in ohmic contact with the AlGaInP-based compound semiconductor. Therefore, a method has been proposed in which an ohmic contact junction electrode made of a material different from the reflective film metal is disposed at a part of the interface between the AlGaInP-based compound semiconductor layer and the reflective metal film to reduce the electrical resistance.

JP 2005-175462 A

  By the way, in the production of the ohmic contact junction electrode, a resist material is patterned by using a general photolithography technique. In the lift-off process after the formation of the ohmic contact bonding electrode, if there is a residue of resist material, it will cause a defective interface bonding of the reflective metal film to be formed later, or a void (gap) after bonding. It is necessary to reliably remove the resist residue later.

It is known that a resist that cannot be removed by a general organic solvent lift-off process is reliably removed by an oxygen plasma ashing method. However, since the resist is removed by oxidation, the ohmic contact junction electrode is also oxidized at the same time. As a result, the resistance at the interface between the oxidized ohmic contact junction electrode and the reflective metal film increases, and the variation in resistance also increases, resulting in a variation in current density in each ohmic contact junction electrode in the LED element. For this reason, current concentration occurs and the forward voltage increases. In addition, there is a problem in that the light emission in the LED element surface becomes non-uniform and the light emission output decreases. Further, when the current density injected into the LED element is increased, the oxide film of the ohmic contact junction electrode is broken and conductive at a certain threshold value, so that the linearity of the current-voltage characteristic is remarkably lowered. As a result, the LED element has poor controllability.

  An object of the present invention is to provide a semiconductor light emitting device that solves the above-described problems and enables high luminance and low forward voltage.

  In order to solve the above problems, the present invention is configured as follows.

According to a first aspect of the present invention, there is provided a group III-V compound semiconductor layer having a structure in which a light emitting layer is sandwiched between a first conductivity type semiconductor layer and a second conductivity type semiconductor layer, and the III-V group compound semiconductor. The first main surface side of the layer is a light extraction surface, formed on the second main surface side of the III-V compound semiconductor layer, and reflects light from the light emitting layer to the first main surface side A reflective metal film having a reflective layer, a conductive support substrate bonded to the III-V compound semiconductor layer via the reflective metal film, the III-V compound semiconductor layer, and the reflective metal film. Ohmic contact junctions distributed at the interface, a surface electrode formed on the first main surface side of the III-V compound semiconductor, and a back electrode formed on the back side of the conductive support substrate And the ohmic contact junction is a group III-V compound. A semiconductor comprising: an ohmic contact metal layer that is in ohmic contact with a conductor layer; and an antioxidant metal layer that is formed in contact with the reflective metal film and contains 90% or more of a metal having an ionization tendency of pure silver or less. It is a light emitting element.

According to a second aspect of the present invention, in the semiconductor light emitting device according to the first aspect, a transparent dielectric film is formed between the III-V compound semiconductor layer and the reflective metal film, and each of the ohmic contact junctions Is provided so as to penetrate the transparent dielectric film and to be in contact with the III-V compound semiconductor layer and the reflective metal film.

  According to a third aspect of the present invention, in the semiconductor light emitting device of the first aspect or the second aspect, the metal whose ionization tendency of the antioxidant metal layer is less than or equal to pure silver is Ag, Pt, or Au. It is characterized by that.

  According to a fourth aspect of the present invention, in the semiconductor light emitting device of any one of the first to third aspects, a diffusion barrier effect is provided between the ohmic contact metal layer and the antioxidant metal layer of the ohmic contact junction. The diffusion prevention metal layer which has this is formed, It is characterized by the above-mentioned.

  According to a fifth aspect of the present invention, in the semiconductor light emitting device according to the fourth aspect, the metal of the diffusion preventing metal layer is any one of Ni, Ti, and Pt.

  According to a sixth aspect of the present invention, in the semiconductor light emitting device according to any one of the first to fifth aspects, the ohmic contact junction is in a region other than the region directly below the surface electrode in the transparent dielectric film. It is arranged.

According to a seventh aspect of the present invention, in the semiconductor light emitting device according to any one of the second to sixth aspects, the layer comprising the ohmic contact junction and the transparent dielectric film and the III-V compound semiconductor layer The ratio of the ohmic contact junction at the interface is 10% or less.

According to an eighth aspect of the present invention, in the semiconductor light emitting device according to any one of the first to seventh aspects, the III-V group of the first conductive type semiconductor layer and the second conductive type semiconductor layer. It is characterized in that the resistance on the main surface side of the compound semiconductor layer is low.

A ninth aspect of the present invention, keep one of the semiconductor light-emitting device of the second to eighth aspect, the material of the transparent dielectric film, and characterized in that SiO 2, _SiN, or the ITO To do.

  According to the present invention, since the antioxidant metal layer is formed in contact with the reflective metal film at the ohmic contact junction, the oxidation of the ohmic contact junction can be prevented, and the resistance at the interface between the ohmic contact junction and the reflective metal film can be reduced. This can be sufficiently reduced, current concentration in the semiconductor light emitting element can be suppressed, light emission in the light emitting element can be made uniform, and a semiconductor light emitting element with high luminance and low forward voltage can be obtained.

Hereinafter, embodiments of a semiconductor light emitting device according to the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing the structure of the light emitting diode (LED bare chip) of this embodiment.

As shown in FIG. 1, the light emitting diode of this embodiment has a structure in which a light emitting layer (active layer) 5 is sandwiched between first conductive type semiconductor layers 3 and 4 and second conductive type semiconductor layers 6 and 7. III-V compound semiconductor layer 11, and the first main surface side of the III-V compound semiconductor layer 11 is the light extraction surface 11.
It is a. The light emitting layer portion of the III-V compound semiconductor layer 11 has an AlGaInP-based, A
Compound semiconductors such as lGaAs, GaN, and InGaAsP are used, and examples of growth substrates for epitaxial growth of these compound semiconductors include GaAs substrates, InP substrates, Ge substrates, and sapphire substrates. The light emitting layer (active layer) 5 may be an undoped bulk layer, or a multiple quantum well structure or a strained multiple quantum well structure.

On the second main surface side of the III-V compound semiconductor layer 11, Al, Ag, Au, etc. for reflecting the light emitted from the light emitting layer 5 toward the second main surface side toward the light extraction surface 11 a side. A reflective metal film 10 having a reflective layer made of the above metal is formed.

The III-V compound semiconductor layer 11 is coupled to and supported by the conductive support substrate 20 via the reflective metal film 10. In the present embodiment, bonding is performed by bonding a bonding layer made of Au or the like of the metal bonding film 21 on the conductive support substrate 20 side and a bonding layer made of Au or the like on the outermost surface of the reflective metal film 10. As the conductive support substrate 20, for example, a Si substrate, a Ge substrate, a GaAs substrate, a metal substrate, or the like is used.

At the interface between the III-V group compound semiconductor layer 11 and the reflective metal film 10, ohmic contact junctions 9 are disposed in a dispersed manner. The ohmic contact junction is also called an ohmic contact junction electrode, an interface electrode, a partial electrode, or the like.
The ohmic contact junction 9 is formed in contact with the reflective metal film 10 and the ohmic contact metal layer 9a for reducing the contact resistance by ohmic contact with the III-V compound semiconductor layer 11, and the ionization tendency is pure silver. And an antioxidant metal layer 9b containing 90% or more of the following metal.
The antioxidant metal layer 9b is a layer for preventing oxidation of the ohmic contact junction 9 due to oxygen plasma ashing or the like during resist removal. Therefore, the antioxidant metal layer 9b is preferably a metal having an ionization tendency of pure silver or less, that is, Ag, Pt, or Au. Further, an alloy may be used for the antioxidant function as long as it is a high-purity metal containing 90% or more of these metals.

A surface electrode 12 is formed on the first conductive type semiconductor layer 3 on the first main surface side of the III-V compound semiconductor 11, and a back electrode 13 is formed on the back surface side of the conductive support substrate 20. Is formed.

In the light emitting diode of the present embodiment, the transparent dielectric film 8 is formed between the III-V compound semiconductor layer 11 and the reflective metal film 10, and each ohmic contact junction 9 has the transparent dielectric film 8. It penetrates and is provided in contact with the III-V compound semiconductor layer 11 and the reflective metal film 10, respectively.
When the III-V compound semiconductor layer 11 and the reflective metal film 10 are in direct contact with each other, the compound semiconductor layer 11 and the reflective metal film 10 react in a bonding process or a heat treatment process after electrode formation. There arises a problem that the reflectance decreases. For this reason, the transparent dielectric film 8 is sandwiched between the compound semiconductor layer 11 and the reflective metal film 10 to prevent a reaction between the compound semiconductor layer 11 and the reflective metal film 10. However, as it is, electrical conduction cannot be performed between the compound semiconductor layer 11 and the reflective metal film 10, so that the ohmic contact junction 9 is disposed on a part of the transparent dielectric film 8. As the transparent dielectric film 8, SiO ₂ , SiN, and ITO (Indium Tin Oxide) that are relatively easy to perform an etching process are desirable in the process step.

The ohmic contact junctions 9 are preferably dispersed and arranged in a region other than the region immediately below the surface electrode 12 in the transparent dielectric film 8. Electrons or holes injected from the surface electrode 12 flow to the support substrate 20 via the ohmic contact junction 9, so that the current confinement can be achieved by not arranging the ohmic contact junction 9 immediately below the surface electrode 12. The effect works and the light output is improved.
In order to make the current confinement effect more effective, the resistance of the semiconductor layer on the main surface side in the first conductive type semiconductor layers 3 and 4 and the second conductive type semiconductor layers 6 and 7 of the compound semiconductor layer 11 is reduced. Low is important. Here, if one of the first conductivity type and the second conductivity type is n-type, the other is p-type. The first conductivity type may be either n-type or p-type.

The ratio of the ohmic contact junction 9 at the interface between the layer composed of the ohmic contact junction 9 and the transparent dielectric film 8 and the III-V compound semiconductor layer 11 is preferably 10% or less. Since the ohmic contact metal layer 9a is a metal having a low reflectance, the area of the ohmic contact junction 9 is preferably small to some extent from the viewpoint of light emission output, and the area ratio at the interface is 10 based on the examination results of the inventors. % Has been found to be desirable.

The ohmic contact bonding portion 9 is formed by patterning a resist material using a general photolithography technique, forming an ohmic contact bonding metal film by a vacuum deposition method, and then removing the resist material by a lift-off method. Since the resist residue needs to be surely removed after the lift-off process, the resist is surely removed by oxygen plasma ashing or the like. At that time, in the conventional ohmic contact junction electrode, the metal surface is oxidized and an oxide film is formed.
Therefore, in this embodiment, the oxidation of the ohmic contact junction 9 is prevented and suppressed by covering the outermost surface of the ohmic contact junction 9 with the formation of the antioxidant metal layer 9b. Since the oxidation of the ohmic contact junction 9 at the time of removing the resist can be prevented, the resistance at the interface between the ohmic contact junction 9 and the metal reflective film 10 can be sufficiently reduced, and each ohmic contact junction 9 in the LED element plane can be reduced. The current density becomes uniform, and the light emission in the LED element surface becomes uniform, and an LED element with high brightness and low forward voltage can be obtained.

In the above embodiment, a diffusion preventing metal layer 9c having a diffusion barrier effect may be formed between the ohmic contact metal layer 9a and the oxidation preventing metal layer 9b of the ohmic contact junction 9. As the metal of the diffusion preventing metal layer 9c, Ni, Ti, and Pt are preferable.
Moreover, in the said embodiment, in order to improve the contact | adhesion power of the ohmic contact metal layer 9a between the ohmic contact junction part 9 and the semiconductor layer 7, the contact | adherence layer, such as Ni, Al, Ti, which has the contact effect, was provided. An ohmic contact junction structure may be used.

Next, examples of the present invention will be described.
Example 1
A replaceable red LED element having the same cross-sectional structure as that of the above embodiment shown in FIG. 1 and an emission wavelength of around 630 nm was produced. The epitaxial growth method, the thickness and structure of the epitaxial layer, the production of the transparent dielectric film / ohmic contact junction / metal reflective film, the method of attaching to the support substrate, the electrode formation method, the LED element production method, etc. are as follows: It is.

A method for manufacturing the LED element of Example 1 will be described with reference to the process chart shown in FIG.
First, as shown in FIG. 3A, a red LED epitaxial wafer was produced. An n-type GaAs substrate 1 is placed in an MOVPE (metal organic vapor phase epitaxy) apparatus, and undoped (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P is formed on the n-type GaAs substrate 1 by the MOVPE method. Etching stop layer 2, Si-doped n-type GaAs contact layer 3, Si-doped n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layer 4, undoped (Al _0.1 Ga _{0 .9} ) _0.
5 In _0.5 P active layer 5, Mg-doped p-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layer 6, and Mg-doped p-type GaP contact layer 7 are sequentially stacked. Grown up.

The growth temperature in MOVPE growth was 650 ° C., the growth pressure was about 6666 Pa (50 Torr), the growth rate of each layer was 0.3 to 1.0 nm / sec, and the V / III ratio was about 200. Incidentally, the V / III ratio referred to here is the ratio (quotient) when the denominator is the number of moles of a group III material such as TMGa or TMAl and the molecule is the number of moles of a group V material such as AsH ₃ or PH _3. Point to.

Examples of raw materials used in the MOVPE growth include trimethylgallium (TMGa), organic metals such as triethylgallium (TEGa), trimethylaluminum (TMAl), and trimethylindium (TMIn), arsine (AsH ₃ ), and phosphine (PH ₃ ). A hydride gas such as was used. Disilane (Si ₂ H ₆ ) was used as an additive material (conductivity type determining impurity) for the n-type semiconductor layer. Biscyclopentadienyl magnesium (Cp ₂ Mg) was used as an additive material for the p-type semiconductor layer.
In addition, hydrogen selenide (H ₂ Se), monosilane (SiH ₄ ), diethyl tellurium (DETe), and dimethyl tellurium (DMTe) can also be used as an n-type additive material for the n-type semiconductor layer. Moreover, dimethyl zinc (DMZn) and diethyl zinc (DEZn) can also be used as a p-type additive material for other p-type semiconductor layers.

Next, after the LED epitaxial wafer was unloaded from the MOCVD apparatus, a SiO ₂ film 8 was formed as a transparent dielectric film on the surface of the p-type GaP contact layer 7 using a plasma-CVD apparatus. Then, using a general photolithographic technique such as a resist or mask aligner, is formed by dispersing an opening of circular cross-section passing through the SiO ₂ film 8 on the SiO ₂ film 8 a hydrofluoric acid etching solution, which opening After forming the ohmic contact bonding part 9 by the vacuum evaporation method, the resist material was removed by the lift-off method (FIG. 3B). The ohmic contact bonding portion 9 was disposed so as to be in a region other than immediately below the surface electrode 12 to be formed in a later step. The arrangement rule was random arrangement, and 40 ohmic contact junctions 9 having a diameter of 7.5 μm were arranged.
The ohmic contact junction 9 of the first embodiment has an ohmic contact metal layer 9a made of AuBe (gold / beryllium alloy) having a thickness of about 88 nm and an antioxidant metal layer 9b made of Au having a thickness of about 30 nm. It is a laminated two-layer structure.

In order to remove the resist residue after the lift-off process, an ashing process was performed using an oxygen plasma ashing apparatus. Ashing was performed in an atmosphere of about 53.3 Pa (400 mTorr) with an output of 600 mW for 20 minutes.

  Next, Al (aluminum), Ti (titanium), and Au (gold) were sequentially deposited as the reflective metal film 10 on the above-described LED epitaxial wafer with an ohmic contact junction (FIG. 3C). Al is a reflective layer, Ti is a diffusion barrier layer, and Au is a bonding layer.

  On the other hand, Ti (titanium), Pt (platinum), and Au (gold) were sequentially deposited on the surface of the conductive Si substrate 20 prepared as a conductive support substrate to form a metal bonding film 21 (FIG. 3D). )). Ti is an ohmic contact metal layer, Pt is a diffusion barrier layer, and Au is a bonding layer.

The Au bonding layer on the outermost surface of the reflective metal film 10 of the epitaxial wafer for LED produced as described above was bonded to the Au bonding layer on the outermost surface of the metal bonding film 21 of the Si substrate 20 (FIG. 3E). . The bonding was performed by holding at a temperature of 350 ° C. for 30 minutes in a pressure of about 1.33 Pa (0.01 Torr) and a load of 30 kgf / cm ² .

Next, the n-type GaAs substrate 1 of the LED epitaxial wafer bonded to the Si substrate 20 is removed by etching with a mixed solution of ammonia water and hydrogen peroxide solution, and undoped (Al _0.7 Ga _0.3 ) _{0. The} In _0.5 P etching stop layer 2 was exposed. Further, the etching stop layer 2 was removed with hydrochloric acid to expose the n-type GaAs contact layer 3.
Further, the surface of the n-type GaAs contact layer 3 is formed using a general photolithography technique such as a resist or a mask aligner, and has a shape having a branch portion radially extending in a branch shape with a width of 10 μm from a circular center portion having a diameter of 100 μm. Electrode 12 was formed by vacuum evaporation. The surface electrode 12 was formed by sequentially depositing AuGe (gold / germanium alloy), Ti (titanium), and Au (gold).

After the surface electrode 12 is formed, the n-type GaAs contact layer 3 other than directly under the surface electrode 12 is removed by etching using an etchant composed of a mixture of sulfuric acid, hydrogen peroxide solution, and water using the formed surface electrode 12 as a mask. Then, the n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 4 was exposed by selective etching.
Further, a back electrode 13 was formed on the entire bottom surface of the Si substrate 20 by vacuum deposition. The back electrode 13 is formed by sequentially depositing Ti (titanium) and Au (gold), respectively, and then an alloying process that is alloying of the electrodes 12 and 13 is heated to 400 ° C. in a nitrogen gas atmosphere for 5 minutes. This was done by heat treatment.

Thereafter, the LED Si substrate 20 on which the electrodes are formed as described above is cut using a dicing device so that the circular portion of the surface electrode 12 is at the center of each chip, and an LED bare chip having a chip size of 300 μm square is formed. It produced (FIG.3 (f)).
Further, the LED bare chip is mounted on the TO-18 stem (die bonding), and then wire bonding is performed on the mounted LED bare chip.
An ED element was produced.
As a result of evaluating the initial characteristics of the LED element manufactured as described above, it was possible to obtain an LED element having initial characteristics of a light emission output of 5.5 mW and a forward voltage of 1.95 V when energized with 20 mA (evaluation). .

(Comparative example)
As a comparative example for comparison with Example 1 described above, a replaceable red LED element having an emission wavelength near 630 nm and having the structure shown in FIG. 2 was produced. The epitaxial growth method, the thickness and structure of the epitaxial layer, the production of the transparent dielectric film / reflective metal film, the method of attaching to the support substrate, the process steps such as the electrode formation method, the etching method, the LED element production method, etc. The same as in Example 1 above. The difference from the first embodiment is the structure of the ohmic contact junction.
In the comparative example, the ohmic contact bonding portion 19 was formed as a single layer ohmic contact metal layer made of AuBe (gold / beryllium alloy) and formed by vacuum deposition.
As a result of evaluating the initial characteristics of the obtained LED element of the comparative example, the light emission output when energized with 20 mA was 4.5 mW and the forward voltage was 2.50 V.

From the results of the above Example 1 and the comparative example, in Example 1, since the oxidation preventing metal layer 9b of Au is formed on the outermost surface of the ohmic contact junction 9, the ohmic contact junction is formed during the oxygen ashing process. 9 It is thought that oxidation of the surface was prevented.
Therefore, since the resistance of the ohmic contact junction 9 is reduced and uniform, the current density at the ohmic contact junction 9 in the LED element surface becomes uniform, current concentration is suppressed, and the forward voltage is reduced. It is thought that. In addition, since the current flows uniformly in the LED element surface, it is considered that the light emission output is also improved.
In FIG. 4, the current-voltage characteristic of Example 1 and a comparative example is shown. As shown in the figure, in Example 1, it can be seen that the linearity of the current-voltage characteristic is good. This also confirms that the partial resistance increase due to the oxide film does not occur in the ohmic contact junction 9.

(Example 2)
A replaceable red LED element having an emission wavelength of about 630 nm and having the structure shown in FIG. 5 was produced. Epitaxial growth method, epitaxial layer thickness and structure, production of transparent dielectric film / ohmic contact junction / reflective metal film, method of attaching to support substrate, electrode forming method, etching method, etc., LED element production The method and the like are basically the same as those in the first embodiment. A different point from the said Example 1 is the structure of an ohmic contact junction part, The difference with the said Example 1 is demonstrated.
The ohmic contact junction 9 of Example 2 is composed of an ohmic contact metal layer 9a made of AuBe having a thickness of about 68 nm, a diffusion preventing metal layer 9c made of Ti having a thickness of about 10 nm, and Au having a thickness of about 30 nm. It has a three-layer structure in which the antioxidant metal layer 9b is sequentially laminated.

  After the ohmic contact junction 9 was formed, oxygen ashing was performed after 168 hours to produce an LED element. As a result of evaluating the initial characteristics of the manufactured LED element of Example 2, it was possible to obtain an LED element having initial characteristics of a light emission output of 5.52 mW and a forward voltage of 1.98 V when energized with 20 mA. This is an equivalent LED characteristic as compared with the initial characteristic of Example 1.

However, in Example 1 above, when the LED element was fabricated by performing oxygen ashing treatment 168 hours after the ohmic contact junction 9 was formed, the initial characteristic of the LED element was a light emission output of 5.2 mW, forward direction. The voltage was 2.25V. This is presumably because Be in the AuBe layer of the ohmic contact metal layer 9a diffuses into the Au layer of the antioxidant metal layer 9b and is easily oxidized at room temperature. That is, in the ohmic contact junction 9 having the two-layer structure of Example 1, it is necessary to perform an oxygen ashing process immediately after the formation of the ohmic contact junction 9 to produce an LED element.
On the other hand, in the ohmic contact junction part 9 of Example 2, the diffusion preventing metal layer 9c of Ti layer acting as a diffusion barrier effect is inserted between the ohmic contact metal layer 9a and the antioxidant metal layer 9b. The Be of the ohmic contact metal layer 9a is prevented from diffusing into the Au layer of the anti-oxidation metal layer 9b, and the purity of the anti-oxidation metal layer 9b of Au on the outermost surface is maintained even after 168 hours have elapsed after the formation of the ohmic contact junction electrode It is thought that it was maintained at a high level and the antioxidant function was maintained. That is, the change with time of the ohmic contact junction 9 can be suppressed by the method shown in Example 2.

  In addition, in the said Example, although the red LED element of emission wavelength 630nm was produced, it is used also in the other LED element produced using the same AlGaInP type material, for example, the LED element of emission wavelength 560nm -660nm. The material and carrier concentration of each layer are the same. Therefore, the same effect can be obtained even when the emission wavelength of the LED element is set to a wavelength band different from that of the above embodiment.

  Moreover, in the said Example, although AuBe was used as the ohmic contact metal layer 9a of the ohmic contact junction part 9, this is because it is suitable for ohmic contact junction with a p-type semiconductor layer, and an n-type semiconductor layer and When the ohmic contact junction is considered, even if AuZn is used as the ohmic contact metal layer, the same effect can be obtained.

1 is a cross-sectional structure diagram of a light emitting diode according to an embodiment of the present invention and Example 1. FIG. It is sectional structure figure of the light emitting diode of a comparative example. 6 is a process diagram illustrating a method for manufacturing the light-emitting diode of Example 1. FIG. It is a graph which shows the current-voltage characteristic of Example 1 and a comparative example. It is sectional drawing of the light emitting diode which concerns on Example 2 of this invention.

Explanation of symbols

1 n-type GaAs substrate 2 n-type AlGaInP etching stop layer 3 n-type GaAs contact layer (first conductivity type semiconductor layer)
4 n-type AlGaInP cladding layer (first conductivity type semiconductor layer)
5 AlGaInP active layer (light emitting layer)
6 p-type AlGaInP cladding layer (second conductivity type semiconductor layer)
7 p-type GaP contact layer (second conductivity type semiconductor layer)
8 SiO ₂ film (transparent dielectric film)
DESCRIPTION OF SYMBOLS 9 Ohmic contact junction part 9a Ohmic contact metal layer 9b Antioxidation metal layer 9c Diffusion prevention metal layer 10 Reflective metal film 11 Compound semiconductor layer 11a Light extraction surface 12 Surface electrode 13 Back surface electrode 20 Si substrate (conductive support substrate)
21 Metal bonding film

Claims (9)

III- having a structure in which a light emitting layer is sandwiched between a semiconductor layer of the first conductivity type and a semiconductor layer of the second conductivity type
A group V compound semiconductor layer;
The first main surface side of the III-V compound semiconductor layer is a light extraction surface, and is formed on the second main surface side of the III-V compound semiconductor layer. A reflective metal film having a reflective layer that reflects to the main surface side of
A conductive support substrate bonded to the III-V compound semiconductor layer via the reflective metal film;
An ohmic contact junction disposed in a dispersed manner at the interface between the III-V compound semiconductor layer and the reflective metal film;
A surface electrode formed on the first main surface side of the III-V compound semiconductor;
A back electrode formed on the back side of the conductive support substrate,
The ohmic contact junction includes an ohmic contact metal layer that is in ohmic contact with the group III-V compound semiconductor layer, and a metal that has an ionization tendency of pure silver or less and is 90% or more. A semiconductor light emitting device comprising an antioxidant metal layer. 2. The semiconductor light emitting device according to claim 1, wherein a transparent dielectric film is formed between the III-V compound semiconductor layer and the reflective metal film, and each ohmic contact junction includes the transparent dielectric film. A semiconductor light-emitting element, which penetrates and is provided in contact with the group III-V compound semiconductor layer and the reflective metal film.   3. The semiconductor light emitting device according to claim 1, wherein a metal whose ionization tendency of the antioxidant metal layer is equal to or lower than pure silver is Ag, Pt, or Au. 4.   4. The semiconductor light emitting device according to claim 1, wherein a diffusion preventing metal layer having a diffusion barrier effect is formed between the ohmic contact metal layer and the antioxidant metal layer of the ohmic contact junction. A semiconductor light emitting device characterized by comprising:   5. The semiconductor light emitting device according to claim 4, wherein the metal of the diffusion preventing metal layer is Ni, Ti, or Pt.   6. The semiconductor light emitting device according to claim 1, wherein the ohmic contact junction is disposed in a region other than a region directly below the surface electrode in the transparent dielectric film. Light emitting element. 7. The semiconductor light emitting device according to claim 2, wherein the ohmic contact junction at an interface between the ohmic contact junction and the layer made of the transparent dielectric film and the III-V compound semiconductor layer is formed. A semiconductor light emitting element characterized by having a ratio of 10% or less. 8. The semiconductor light emitting device according to claim 1, wherein a resistance of the first conductive type semiconductor layer and the second conductive type semiconductor layer on a main surface side of the III-V group compound semiconductor layer is set. A semiconductor light emitting device characterized by being low. The semiconductor light emitting device according to any one of claims 2-8, the material of the transparent dielectric film, SiO 2, _SiN, a semiconductor light emitting device characterized in that either ITO.

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