JP4232281B2 - AlGaInP light emitting diode - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a structure of a high-brightness AlGaInP light-emitting diode, and more particularly to an AlGaInP light-emitting diode having a window layer made of a transparent and conductive metal oxide.
[0002]
[Prior art]
As a green, yellow to red-orange light emitting element, an AlGaInP light emitting diode (LED) having a pn junction type double hetero (DH) structure light emitting portion made of an aluminum phosphide / gallium / indium (AlGaInP) mixed crystal is known. (See Appl. Phys. Lett., 61 (15) (1992), pages 1775-1777).
In particular, aluminum phosphide, gallium indium to about 0.5 indium composition ratio _{((Al α Ga 1- α)} 0.5 In 0.5 P: 0 ≦ α ≦ 1) is good and gallium arsenide (GaAs) single crystal (See Appl. Phys. Lett., 57 (27) (1990), pages 2937 to 2939), and a clad layer or a light emitting layer (active layer) forming a light emitting portion of a DH structure. (See Appl. Phys. Lett., 58 (10) (1991), pages 1010 to 1012).
[0003]
An LED having an n-type layer as a cladding layer on the side where light emitted from the light emitting layer in the opposite direction to the substrate is referred to as an n-side-up type LED, and an LED having a p-type layer as a p-side-up type LED.
In either the n-side-up type or the p-side-up type, in the conventional AlGaInPLED, a window layer (window layer) for efficiently extracting light emitted from the light emitting portion to the outside is formed on the upper cladding layer. (See SPIE, Vol . 3002 (1997), pages 110-118).
The window layer must be made of a material having a large forbidden band width that is transparent to light emission. In the conventional AlGaInPLED, the window layer is made of an aluminum gallium arsenide (Al _C Ga _{1 -C} As: 0 ≦ C ≦ 1) crystal. (See Appl. Phys. Lett., 58 (1991) above). In addition, an example composed of gallium phosphide (GaP) is also known (see J. Electron. Mater., 20 (1991), pages 1125 to 1130). Also disclosed is a technique for forming a window layer from gallium arsenide phosphide (GaAsP), gallium phosphide indium (GaInP) or aluminum gallium gallium indium (AlGaInP) (Japanese Patent Laid-Open No. 11-17220). Refer to the book)
[0004]
As a material for the window layer of AlGaInPLED, in addition to the III-V group compound semiconductor material as described above, for example, US Pat. No. 5,481,122 discloses indium-tin oxide (abbreviated as ITO). A translucent metal oxide window layer is described. Furthermore, according to JP-A-11-17220, a conductive and translucent metal oxide layer made of indium oxide / tin oxide, indium oxide, tin oxide, zinc oxide or magnesium oxide is formed by gallium phosphide (GaP ), Gallium arsenide phosphide (GaAsP), gallium arsenide phosphide (GaInP), or means for providing on a contact layer made of gallium arsenide (GaAs).
[0005]
[Problems to be solved by the invention]
However, in particular for emitting a green light _{(Al α Ga 1- α) 0.5} In 0.5 P (0 ≦ α ≦ 1) In AlGaInPLED having a light emitting layer, the group III-V compound semiconductor when used in window layer In addition, since the forbidden band width is small, there is a problem that light emitted from the light emitting layer is absorbed by the window layer.
[0006]
In addition, in a window layer having a structure in which a metal oxide layer such as ITO is laminated on a III-V compound semiconductor layer, a low ohmic contact resistance is stable between the compound semiconductor layer and the metal oxide layer. It has been a practical problem that it cannot be obtained.
For this reason, it is necessary to use a semiconductor layer having a high carrier concentration exceeding about 1 × 10 ¹⁹ cm ⁻³ for the III-V compound semiconductor layer on which the metal oxide layer is laminated (Japanese Patent Laid-Open No. Hei 11). -17220). However, when a high concentration impurity is doped in the III-V compound semiconductor layer in order to obtain the III-V compound semiconductor layer having a high carrier concentration as described above, the crystallinity of the III-V compound semiconductor layer is deteriorated. It is customary. For this reason, it is not easy to obtain a III-V group compound semiconductor layer having a high carrier concentration, a low crystal defect density, and an excellent specific resistance and mobility.
[0007]
In general, in a metal oxide such as zinc oxide, the higher the carrier concentration, that is, the lower the specific resistance, the lower the translucency. Therefore, when the metal oxide layer has a high carrier concentration in order to obtain ohmic contact with the semiconductor layer, the translucency of the window layer made of the metal oxide layer is lowered.
For this reason, in order to satisfy both the electrode characteristics of the window layer made of metal oxide and the extraction efficiency of light emission to the outside, the carrier concentration and specific resistance of the window layer made of metal oxide are specified. It was necessary to install.
[0008]
In addition, depending on the type of the light-transmitting metal oxide, the formation of the electrode may be hindered. For example, zinc oxide (ZnO), which is one of translucent metal oxides, is an amphoteric oxide and easily dissolves in both acids and alkalis ("Iwanami Physical and Chemical Dictionary 3rd Edition" (Iwanami Shoten, 1976). Issued April 5th, 7th edition, 3rd edition), page 508). For this reason, when the metal oxide layer made of zinc oxide is exposed as the outermost layer of the window layer, there is a problem that the zinc oxide layer is dissolved and disappears by an acidic or alkaline etching agent accompanying a general photolithography process or the like. .
[0009]
The above summarizes the problems of the prior art.
(A) In a window layer made of a III-V group compound semiconductor, the forbidden band width is not sufficiently large, so that the green light emission from the AlGaInP light emitting layer cannot be transmitted to the outside sufficiently efficiently,
(B) In a structure in which a window layer made of a transparent metal oxide is provided on the III-V group compound semiconductor layer, a high carrier concentration and a low specific resistance are brought into contact with the window layer made of a metal oxide. It is difficult to form a III-V compound semiconductor layer having excellent crystallinity of
(C) If the metal oxide layer has a high carrier concentration, the translucency of the metal oxide layer decreases, and the metal oxide should be provided as a window layer that satisfies both ohmic characteristics and translucency for light emission. The preferred range such as the carrier concentration of the layer is unknown,
(D) Depending on the type of the metal oxide layer, there is difficulty in processing associated with the formation of the ohmic electrode, and in particular, the window layer having a structure in which the metal oxide layer made of zinc oxide is exposed as the outermost layer of the window layer. Then, it is mentioned that the loss | disappearance of zinc oxide cannot be avoided easily on an electrode formation process.
[0010]
The present invention has been made to overcome the above-described problems of the prior art, and an object of the present invention is to provide an n-side-up type AlGaInPLED having a window layer made of a transparent and conductive metal oxide.
(1) It is possible to efficiently extract emitted light to the outside,
(2) A good ohmic contact can be obtained with a low resistance and a III-V compound semiconductor layer,
(3) Excellent translucency for green to red light,
(4) To present a structure of a window layer made of a metal oxide capable of forming an electrode with a normal processing technique.
[0011]
[Means for Solving the Problems]
In the present invention, the object of (1) is solved by a laminated structure of metal oxide layers invented in view of the refractive index. Further, the objects (2) and (3) are solved by defining the electrical characteristics and transmittance of the window layer constituent material.
That is, the invention of claim 1 of the present application is a substrate made of a p-type gallium arsenide (GaAs) single crystal and a p-type lower clad made of an aluminum gallium phosphide / indium (AlGaInP) mixed crystal sequentially laminated on the substrate. In an AlGaInP light emitting diode comprising: a light emitting portion composed of a layer, a light emitting layer, and an n-type upper cladding layer; and a window layer made of a transparent and conductive metal oxide layer provided on the light emitting portion The window layer is provided on a side opposite to the light emitting portion of the first metal oxide layer having a _first refractive index n ₁ provided on the light emitting portion side and the first metal oxide layer. And a second metal oxide layer having a _second refractive index n ₂ (n ₁ > n ₂ ) smaller than the first refractive index.
[0012]
The invention according to claim 2 is the AlGaInP light emitting diode according to claim 1, wherein the first metal oxide layer is separately formed on the light emitting part or the light emitting part. The first metal oxide layer is made of zinc oxide (ZnO), and the second metal oxide layer is made of a composite oxide of indium (In) oxide and tin (Sn) oxide. It is characterized by becoming.
[0013]
The invention according to claim 3 is the AlGaInP light emitting diode according to claim 2, wherein the carrier concentration of the zinc oxide layer constituting the first metal oxide layer is 5 × 10 ¹⁹ cm ⁻³ or more and 7 ×. It is characterized by being 10 ²⁰ cm ⁻³ or less.
[0014]
The invention of claim 4 is the AlGaInP light emitting diode according to claim 2, wherein the zinc oxide layer constituting the first metal oxide layer has a specific resistance of 1 × 10 ⁻⁴ Ω · cm 3 or more. × 10 ⁻³ Ω · cm or less.
[0015]
According to a fifth aspect of the present invention, there is provided a substrate made of a semiconductor single crystal, a light emitting portion made of an aluminum phosphide / gallium / indium (AlGaInP) mixed crystal sequentially stacked on the substrate, and the light emitting portion. In an AlGaInP light emitting diode comprising a transparent and conductive metal oxide layer, the window layer is composed of a plurality of metal oxide layers, and the plurality of metal oxide layers are formed from a light emitting layer. The refractive index is arranged so that the refractive index gradually decreases as the distance is increased in the light emission extraction direction.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the window layer is formed by stacking at least two transparent and conductive metal oxide layers having different refractive indexes. When the window layer is composed of two metal oxide layers, the first metal oxide layer on the side closer to the light emitting portion of the AlGaInP light emitting diode has a refractive index n _1. A metal oxide layer having a refractive index n ₂ (n ₁ > n ₂ ) smaller than n ₁ , wherein the second oxide layer provided on the side opposite to the light emitting portion of the _first metal oxide layer Consists of.
In the present invention, the window layer may be composed of three or more metal oxide layers. For example, when the window layer is composed of three metal oxide layers, the third oxide layer provided on the opposite side of the second metal oxide layer from the first oxide layer is the second metal oxide layer. It is composed of a metal oxide layer having a refractive index smaller than the refractive index n _{2 of the} oxide layer. That is, in the present invention, the window layer is composed of a plurality of transparent and conductive metal oxide layers, and the plurality of metal oxide layers have a refractive index sequentially as the distance from the light emitting layer is increased in the light emission extraction direction. A metal oxide material is selected so as to be small. As described above, the window layer having a refractive index distribution such that the refractive index gradually decreases in the light extraction direction has an effect of efficiently extracting light emitted from the light emitting layer to the outside.
[0017]
Of the metal oxide layers constituting the window, the metal oxide layer provided closest to the light emitting portion made of an aluminum phosphide / gallium / indium (AlGaInP) mixed crystal has a refractive index smaller than that of AlGaInP. It is preferably composed of a metal oxide.
[0018]
Further, when a window layer is formed on an n-type III-V group compound semiconductor layer serving as a surface in the light extraction direction of an n-side-up type AlGaInPLED, the window layer is a metal oxide exhibiting n-type conductivity. It is preferable to comprise.
In particular, when the first metal oxide layer is formed in contact with the light emitting part or the III-V group compound semiconductor layer separately formed on the light emitting part, the first metal oxide layer on the light emitting part side is: It is desirable to make it from n-type zinc oxide (ZnO) having a refractive index of about 2.0. Since zinc oxide has a low resistance when doped with a group III element at a concentration of several weight percent (wt.%), It is separately formed on the n-type light emitting portion or the light emitting portion that becomes the surface in the light extraction direction. Good ohmic contact with the III-V compound semiconductor layer is achieved.
Note that the metal oxide layer made of zinc oxide is 50 wt. % Or more zinc oxide may be included as a component. For example, 50 wt. The first metal oxide layer may be formed of an indium zinc oxide composite oxide containing at least% and containing the remainder as indium oxide.
[0019]
The second metal oxide layer provided on the side opposite to the light emitting portion of the first metal oxide layer is a composite oxide of indium (In) oxide and tin (Sn) oxide (indium / tin oxide). : ITO).
ITO has a refractive index of about 1.9. For this reason, the window layer in which the first metal oxide layer is made of zinc oxide and the second metal oxide layer is made of ITO is particularly advantageous for taking out light emission to the outside.
Further, the second metal oxide layer made of ITO covers the zinc oxide layer, which is the first metal oxide layer, so that it is possible to prevent the zinc oxide layer having relatively weak chemical resistance from being exposed to the surface. As described above, when the ITO layer functions as a protective layer for the zinc oxide layer, it is possible to avoid the zinc oxide layer from being dissolved or disappeared by etching or the like in the element fabrication process, and to stably manufacture the LED.
[0020]
The n-type zinc oxide layer that forms the first oxide layer is a layer that plays a role of making ohmic contact with a light emitting portion made of AlGaInP mixed crystal or a III-V group compound semiconductor layer separately formed on the light emitting portion. Of course, it is preferable to increase the carrier concentration. However, the electrical specifications of the zinc oxide layer exhibiting n-type conduction and having a suitable ohmic contact with the light emitting part made of AlGaInP mixed crystal or the III-V group compound semiconductor layer separately formed on the light emitting part are as follows: It was not known before.
In the present invention, the preferred carrier concentration range of the zinc oxide layer formed in contact with the light emitting part or the III-V group compound semiconductor layer separately formed on the light emitting part is about 5 × 10 ¹⁹ cm ⁻³ or more and 7 × found that is 10 ²⁰ cm ^-3 or less. A more preferable carrier concentration range is 8 × 10 ¹⁹ cm ⁻³ or more and 5 × 10 ²⁰ cm ⁻³ or less. The carrier concentration of the zinc oxide layer is obtained by a usual Hall effect measurement method.
[0021]
The zinc oxide layer can be formed by a general high-frequency sputtering method, a metal organic chemical vapor deposition method (MOCVD method), or a laser ablation method.
However, if a zinc oxide layer mainly composed of a single crystal is to be formed by the above growth means, the temperature of the substrate is forced to be higher than 500 ° C. At such a high temperature, a zinc oxide layer having excellent conductivity cannot be stably formed.
In the present invention, in order to obtain a zinc oxide layer having good conductivity, the first metal oxide layer is preferably composed of a polycrystalline or amorphous zinc oxide layer. The term “polycrystal” refers to a single crystal and an amorphous mixture or a single crystal aggregate having different orientations. In particular, in a hexagonal wurtzite crystal type zinc oxide, a polycrystalline zinc oxide layer consisting of an aggregate of single crystals grown predominantly in the C-axis direction diffuses the LED drive current in the horizontal (horizontal) direction. This function is remarkable and can be preferably used as a constituent material of a window layer having a current spreading action.
[0022]
In order to obtain an n-type zinc oxide layer having a high carrier concentration, for example, it is necessary to add a group III element such as aluminum (Al), gallium (Ga), or indium (In) as impurities to zinc oxide at a high concentration. is there.
However, when the above impurities are added at a high concentration, the crystallinity of the zinc oxide layer is deteriorated, and accordingly, the light transmittance in the visible light band is also lowered. The degree of crystallinity is measured as the degree of electron mobility and the related specific resistance. Therefore, in the present invention, in order to ensure a high light transmittance in the visible light band, particularly in the visible light band from green to red with a wavelength of about 510 nm to about 650 nm, which can be emitted from the AlGaInP mixed crystal, oxidation is performed. The specific resistance of the zinc layer is preferably in the range of 1 × 10 ⁻⁴ Ω · cm to 3 × 10 ⁻³ Ω · cm. A zinc oxide layer having a specific resistance exceeding 3 × 10 ⁻³ Ω · cm gives an average light transmittance of 80% or more in the above visible light band. Since ohmic contact with the III-V group compound semiconductor layer separately formed on the part deteriorates, it is not preferable.
[0023]
From the n-type zinc oxide layer having the carrier concentration and specific resistance defined as described above, the light transmittance of 80% or more on average in the visible light band from green to red having a wavelength of about 510 nm to about 650 nm is obtained. The 1st metal oxide layer which has can be comprised.
Since the transmittance decreases when the thickness of the first metal oxide layer is increased, the thickness of the first oxide layer is preferably within about 1 μm. Further, if the thickness of the first metal oxide layer is extremely reduced, the light emitting portion or the entire surface of the III-V group compound semiconductor layer separately formed on the light emitting portion is not sufficiently covered, and ohmic contact is not achieved. Non-uniformity is increased, which hinders obtaining an LED having a uniform forward voltage. For this reason, the thickness of the first metal oxide layer needs to be at least about 2 nm.
Further, the preferred range of the carrier concentration, specific resistance and layer thickness of the ITO layer constituting the second metal oxide layer is substantially the same as that of the zinc oxide constituting the first metal oxide layer. From the window layer composed of the multilayer structure of the zinc oxide layer and the ITO layer having the specifications in the preferable range as described above, a window layer exhibiting an average light transmittance of 80% or more in the above wavelength range is provided. Brought about.
[0024]
[Action]
A window layer having a refractive index distribution in which the refractive index is gradually reduced in the direction of taking out light emission facilitates the action of efficiently taking out light emission to the outside.
[0025]
The first metal oxide layer made of zinc oxide has a function of bringing about a low resistance contact in the ohmic contact with the light emitting portion made of AlGaInP or the III-V group compound semiconductor layer separately formed on the light emitting portion.
[0026]
The second metal oxide layer made of ITO constitutes a transparent and conductive window layer together with the first metal oxide layer, and acts as a transparent protective layer for the first metal oxide layer.
[0027]
【Example】
Hereinafter, the present invention will be described in detail based on an example in which an AlGaInPLED is fabricated. FIG. 1 is a schematic diagram showing a cross-sectional structure of an LED according to this example.
[0028]
On a zinc-doped p-type GaAs single crystal substrate 101 having a (001) plane inclined by 4 ° in the [110] direction, a Zn-doped p-type GaAs buffer layer 102 and a Zn-doped p-type (Al _0.7 Ga _0.3 ) _0.5 lower clad layer 103 composed of an in _0.5 P, undoped n-type a _{(Al 0.2 Ga 0.8) 0.5 in} 0.5 emitting layer 104 composed of P mixed crystal were sequentially laminated.
The hole concentration of the p-type lower cladding layer 103 was about 1 × 10 ¹⁸ cm ⁻³ and the layer thickness was about 1 μm. The layer thickness of the light emitting layer 104 was about 150 nm, and the electron concentration was about 5 × 10 ¹⁶ cm ⁻³ .
[0029]
On the light emitting layer 104, an n-type upper clad layer 105 was laminated. The upper clad layer 105 is formed by stacking first to third n-type layers 105a, 105b, and 105c having different electron concentrations.
The first n-type layer 105a is composed of an n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P layer having a thickness of about 1 μm doped with silicon (Si) and an electron concentration of 7 × 10 ¹⁷ cm ^−3. did. The second n-type layer 105b was composed of an n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P layer having a Si-doped layer thickness of 100 nm and an electron concentration of 9 × 10 ¹⁶ cm ⁻³ . The third n-type layer 105c is composed of an n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P layer having a layer thickness of 50 nm doped with selenium (Se) and an electron concentration of 2 × 10 ¹⁹ cm ^−3. did.
The buffer layer 102, the p-type lower cladding layer 103, the light emitting layer 104, and the n-type upper cladding layer 105 are made of trimethylaluminum ((CH ₃ ) ₃ Al), trimethylgallium ((CH ₃ ) ₃ Ga), and trimethylindium ( Lamination was performed at 720 ° C. by a reduced MOCDV method using (CH ₃ ) ₃ In) as a Group III element material and phosphine (PH ₃ ) as a Group V element material. Diethyl zinc ((C ₂ H ₅ ) ₂ Zn), disilane (Si ₂ H ₆ ), and hydrogen selenide (H ₂ Se) were used as the doping materials for zinc, silicon, and selenium.
[0030]
On the third n-type layer 105c forming the surface of the n-type upper cladding layer 105, a first metal oxide layer made of aluminum (Al) -doped n-type zinc oxide (ZnO) is formed by a general high-frequency sputtering method. 106a was deposited. The carrier concentration of the first metal oxide layer 106a at room temperature was about 3 × 10 ²⁰ cm ⁻³ , the specific resistance was about 3 × 10 ⁻³ Ω · cm, and the layer thickness was about 250 nm. The carrier mobility of the first metal oxide layer 106a was about 12 cm ² / V · s. The sheet resistance was about 56Ω / □. A general X-ray diffraction analysis method shows that the zinc oxide layer forming the first metal oxide layer is a polycrystal composed of an aggregate of single crystals grown in the <0001> direction (C axis). It was.
[0031]
A second metal oxide layer 106b made of ITO was stacked on the first metal oxide layer 106a. The carrier concentration of the second metal oxide layer 106b was about 1 × 10 ²⁰ cm ⁻² and the specific resistance was about 4 × 10 ⁻⁴ Ω · cm. The layer thickness was about 200 nm. The window layer 106 is composed of first and second metal oxide layers 106a and 106b.
[0032]
On the window layer 106, a circular n-type electrode 107 made of aluminum (Al) having a diameter of about 110 μm was provided by using a general photolithography technique. Since the window layer 106 has a structure in which the zinc oxide layer is covered with the ITO layer, the zinc oxide layer did not disappear even when the n-type electrode 107 was formed by etching with hydrochloric acid (HCl).
Further, a gold / zinc alloy (Au 98 wt% -Zn 2 wt% alloy) is vacuum-deposited on the entire back surface of the GaAs substrate 101 and then alloyed (alloyed) at 420 ° C. for 2 minutes to form the p-type electrode 108. Was established. Then, it cut | judged into the square chip | tip which makes one side about 350 micrometers, and produced LED.
[0033]
When a current of 20 mA was passed between the n-type electrode 107 and the p-type electrode 108 in the forward direction, red-orange light emission was obtained from almost the entire surface of the LED window layer 106. The peak wavelength of the emission measured by a spectroscope was about 620 nm. Further, the half width of the emission spectrum was about 18 nm, and light emission excellent in monochromaticity was obtained.
Further, the forward voltage when a forward current of 20 mA was passed was about 1.95V. Further, the change width of the forward voltage between the LEDs is about 1.95 V ± 0.04 V, and the forward voltage is made uniform. The emission intensity of the LED reached about 48 milli candela (mcd).
[0034]
【The invention's effect】
In an AlGaInP light emitting diode having a window layer made of a metal oxide layer, if the window layer has a structure having a distribution in the refractive index as described above, the emission extraction efficiency is high, that is, the luminance is high and the emission is monochromatic. A high-performance AlGaInP light-emitting diode having excellent performance and a uniform forward voltage is provided.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a cross-sectional structure of an LED according to an embodiment of the present invention.
[Explanation of symbols]
101 p-type GaAs single crystal substrate 102 p-type GaAs buffer layer 103 p-type lower cladding layer 104 light-emitting layer 105 upper cladding layer 105a first n-type layer 105b second n-type layer 105c third n-type layer 106 window layer 106a First metal oxide layer 106b Second metal oxide layer 107 n-type electrode 108 p-type electrode

Claims (5)

A substrate made of p-type gallium arsenide (GaAs) single crystal, and a p-type lower clad layer, a light emitting layer, and an n-type upper clad layer made of an aluminum phosphide / gallium / indium (AlGaInP) mixed crystal sequentially stacked on the substrate In an AlGaInP light emitting diode comprising a light emitting part composed of a window layer made of a transparent and conductive metal oxide layer provided on the light emitting part, the window layer is on the light emitting part side A first metal oxide layer having a _first refractive index n ₁ and a second refractive index smaller than the first refractive index provided on the opposite side of the light emitting portion of the first metal oxide layer. An AlGaInP light emitting diode comprising a second metal oxide layer having a refractive index n ₂ (n ₁ > n ₂ ). The first metal oxide layer is formed in contact with the light emitting portion or a group III-V compound semiconductor layer separately formed on the light emitting portion, and the first metal oxide layer is made of zinc oxide (ZnO). The AlGaInP light emitting diode according to claim 1, wherein the second metal oxide layer is made of a composite oxide of indium (In) oxide and tin (Sn) oxide. 3. The AlGaInP emission according to claim 2, wherein a carrier concentration of the zinc oxide layer constituting the first metal oxide layer is 5 × 10 ¹⁹ cm ⁻³ or more and 7 × 10 ²⁰ cm ⁻³ or less. diode. 3. The AlGaInP according to claim 2, wherein the zinc oxide layer constituting the first metal oxide layer has a specific resistance of 1 × 10 ⁻⁴ Ω · cm to 3 × 10 ⁻³ Ω · cm. Light emitting diode. A substrate made of a semiconductor single crystal, a light emitting portion made of an aluminum phosphide / gallium / indium (AlGaInP) mixed crystal sequentially stacked on the substrate, and a transparent and conductive metal oxide provided on the light emitting portion In an AlGaInP light emitting diode having a window layer made of a material layer, the window layer is made of a plurality of metal oxide layers, and the plurality of metal oxide layers are spaced apart from the light emitting layer in the direction of light emission extraction. The AlGaInP light-emitting diodes are arranged so that the refractive index becomes smaller sequentially.

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