JP4270652B2 - AlGaInP light emitting diode - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high-brightness AlGaInP light-emitting diode having an upper clad layer including three layers having different electron concentrations and a metal oxide window layer.
[0002]
[Prior art]
As a light-emitting element in the green, yellow to red-orange band, an aluminum phosphide-gallium-indium (AlGaInP) light-emitting diode (LED) having a pn junction type double hetero (DH) junction structure is known (Appl. Phys. Lett., 61 (15) (1992), pages 1775-1777). In particular, the indium composition ratio is about _{0.5 (Al α Ga 1- α)} 0.5 In 0.5 P (0 ≦ α ≦ 1) is also an advantage that play a gallium arsenide (GaAs) single crystal good lattice matching with (See Appl. Phys. Lett., 57 (27) (1990), pages 2937 to 2939) to form a clad layer and a light emitting layer (active layer) constituting the light emitting portion of the DH junction structure. (See Appl. Phys. Lett., 58 (10) (1991), pages 1010-1012).
[0003]
An LED having an n-type cladding layer on the side from which light is extracted is referred to as an n-side-up type, and a p-type layer is referred to as a p-side-up type. In any of the layered structure, clad layers sandwiching the light emitting layer, over a wide range of light-emitting layer, for the purpose of passing a device operation current, doped with an n-type or p-type impurity at a high concentration _(Al α Ga _1- α ) _0.5 In _0.5 P (0 ≦ α ≦ 1) is usually used (see JP-A-2-168690). In general, the electron concentration or hole concentration in the clad layer is generally constant (see Japanese Patent Application Laid-Open No. 2-260682).
[0004]
In the conventional AlGaInP high-intensity LED, a window layer (window layer) for efficiently extracting light emitted from the light emitting portion to the outside is disposed above the upper clad layer (SPIE, Vol. 3002 ( 1997), see pages 110-118). The window layer must be made of a semiconductor material that is transparent to light emission and has a large forbidden band. Conventionally, the window layer is made of aluminum arsenide / gallium crystal (Al _C Ga _{1 -C} As: 0 ≦ C ≦ 1). Examples (see Appl. Phys. Lett., 58 (1991) above), examples composed of gallium phosphide (GaP), etc. are disclosed (J. Electron. Mater., 20 (1991), 1125). (See page 1130).
[0005]
In addition to the III-V compound semiconductor material, for example, in US Pat. No. 5,481,122, a metal oxide window layer made of indium-tin oxide (abbreviated as ITO) is disposed. Further, a means for providing a transparent oxide layer made of indium oxide, tin oxide, zinc oxide or magnesium oxide film is disclosed (see Japanese Patent Application Laid-Open No. 11-17220). Some metal oxides have a high room-temperature forbidden band exceeding 3 electron volts (eV), and are superior in extracting light emission to the outside as compared with III-V group compound semiconductors, which are conventional constituent materials of window layers. ing.
[0006]
A transparent window layer made of a metal oxide that has n-type conductivity, such as ITO, n-type _{(Al α Ga 1- α) 0.5} In 0.5 P (0 ≦ α ≦ 1) comprising by bonding on the upper cladding layer from A problem in providing the metal oxide layer is that a metal oxide layer having a low ohmic contact resistance cannot be stably formed. For this reason, conventionally, a contact layer having a high n-type carrier concentration (= electron concentration) exceeding about 1 × 10 ¹⁹ cm ⁻³ is usually disposed on the n-type cladding layer (see above). JP-A-11-17220). The contact layer is made of gallium phosphide / arsenic (GaAsP), gallium phosphide (GaP), gallium phosphide / indium (GaInP), or gallium arsenide (GaAs) (see the above-mentioned JP-A-11-17220). ), The structure of the laminated structure is complicated, which is a problem.
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described problems of the prior art, and provides a high-brightness LED with a simple laminated structure in an n-side-up type AlGaInP light-emitting diode having a window layer made of a metal oxide. There is.
[0008]
[Means for Solving the Problems]
The inventors of the present invention have reached the present invention as a result of intensive studies to solve the above problems. That is, the present invention is represented by [1] in the p-type GaAs single crystal substrate, respectively _{(Al X Ga 1-X)} Y In 1-Y P (0 ≦ X ≦ 1,0 ≦ Y ≦ 1) p An n-type upper cladding layer in a light-emitting diode having a lower cladding layer, a light-emitting layer, and an n-type upper cladding layer (including cases where the mixed crystal ratios X and Y are different between the respective layers) and a window layer made of a metal oxide However, three layers having different electron concentrations (including the case where the mixed crystal ratios X and Y are different among the three layers, and in order from the layer closer to the light emitting layer, the first n-type layer (the electron concentration is n1, the layer thickness is d2), a second n-type layer (referred to as electron concentration n2, layer thickness d2), and a third n-type layer (referred to as electron concentration n3, layer thickness d3), A light-emitting diode characterized by n3>n1> n2 in the electron concentration of the three layers, [2] p-type lower cladding layer, light-emitting layer The In mixed crystal ratio (1-Y) of the n-type upper cladding layer is 0.5, respectively. The light-emitting diode according to [1], wherein the [3] window layer is a third n The light-emitting diode according to [1] or [2], wherein [4] the first to third n-type layers have a thickness relationship of d1> d3 ≧ d2. [1] The light-emitting diode according to any one of [1] to [3], [5] the electron concentration of the second n-type layer is 1 × 10 ¹⁶ cm ⁻³ ≦ n2 ≦ 5 ×. The light-emitting diode according to any one of [1] to [4], [10] wherein the second n-type layer has a thickness of 20 nm ≦ d2 ≦ 200 nm, which is 10 ¹⁷ cm ^−3. [1] The light-emitting diode according to any one of [1] to [5], wherein [7] the dopant of the first and second n-type layers is Si. [3] The light-emitting diode according to any one of [1] to [6], wherein the dopant of the third n-type layer is Se or Te, and [8] the window layer has n-type conductivity. The light-emitting diode according to any one of [1] to [7], wherein [9] the window layer is formed of indium oxide / tin oxide, indium oxide, tin oxide, zinc oxide, and magnesium oxide The light-emitting diode according to any one of [1] to [8], comprising at least one selected from the group consisting of: [10] The light-emitting diode according to [9], wherein the zinc oxide constituting the window layer includes any one of aluminum, gallium, and indium. [11] Any one of [1] to [10], wherein the hole concentration of the p-type GaAs single crystal substrate is in the range of 5 × 10 ^{18 to} 5 × 10 ¹⁹ cm ^−3. The light emitting diode was used.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIG. In _{(Al X Ga 1-X)} Y In Y P (0 ≦ X ≦ 1,0 ≦ Y ≦ 1) light emitting diode of the present invention, a GaAs single crystal substrate particularly when about 0.5 indium composition ratio Good lattice matching can be obtained.
[0010]
The substrate, but a p-type GaAs single crystal substrate, is convenient if the conductive substrate is for element processing, the hole ^{concentration, 5 × 10 18 ~5 × 10} 19 cm -3 It is preferable that it is the range of these.
[0011]
In the present invention, an n-type (Al _x Ga _{1 -x} ) _0.5 In _0.5 P (0 ≦ X ≦) disposed between the light emitting layer 104 and the window layer 106 made of a metal oxide semiconductor exhibiting n-type conduction. The upper clad layer 105 made of 1) is composed of three layers 105a to 105c having different electron concentrations. The electron concentration of the first n-type layer 105a on the n-type or p-type light emitting layer 104 side is preferably 1 × 10 ¹⁷ cm ⁻³ or more and 5 × 10 ¹⁸ cm ⁻³ or less. When the n-type layer 105a is a high carrier concentration layer doped with a large amount of n-type impurities, a large amount of n-type impurities diffuse into the light-emitting layer 104, and the composition between the light-emitting layer 104 and the n-type layer 105a. This is not preferable because the steepness of light is deteriorated and the monochromaticity of light emission is impaired. The electron concentration of the n-type layer 105a can be achieved by doping a Group IV impurity such as Si or Sn or a Group VI impurity such as Se or Te. For the purpose of suppressing the diffusion of the n-type impurity into the light emitting layer 104, Si having a smaller diffusion constant than the Group VI impurity is a more suitable dopant.
[0012]
The electron concentration of the second n-type (Al _X Ga _{1 -X} ) _0.5 In _0.5 P (0 ≦ X ≦ 1) layer 105b is less than the first electron concentration. Further, the electron concentration of the first n-type layer is set to be lower than the electron concentration of the third n-type layer 105c described later. If the electron concentration of the second n-type layer 105b is made smaller than those of the first and third n-type layers 105a and 105c, it flows from the third n-type layer 105c through the window layer 106 from the electrode 107. It becomes a resistor against the element driving current. That is, the driving current can be diffused over a wide range of the light emitting layer 104.
[0013]
The optimum range of the electron concentration of the second n-type layer 105b is 1 × 10 ¹⁶ cm ⁻³ or more and 5 × 10 ¹⁷ cm ⁻³ or less. If the electron concentration is less than 1 × 10 ¹⁶ cm ⁻³ , the forward voltage becomes too high, and if it exceeds 5 × 10 ¹⁷ cm ⁻³ , the resistance decreases and the driving current cannot be diffused over a wide range. The electron concentration in the optimum range is determined by taking the (Al _x Ga _{1 -x} ) _0.5 In _0.5 P (0 ≦ X ≦ 1) layer forming the second n-type layer 105b as an example, and using an organometallic pyrolysis (MO − In some cases, the CVD method may be used in an undoped state in which n-type impurities are not intentionally added. However, if the Group IV or Group VI element is an n-type dopant and the doping amount is adjusted, the electron concentration can be controlled more stably. As the n-type dopant, Si, which does not easily diffuse, is suitable as in the case of the first n-type layer 105b in order to reduce the amount of the dopant penetrating into the light emitting layer 104.
[0014]
The layer thickness of the second n-type layer 105b is equal to or less than the layer thickness of the third n-type layer, and the third n-type layer is less than the layer thickness of the first n-type layer. Is preferred. If the thickness of the second n-type layer is greater than or equal to the thickness of the first n-type layer, the forward voltage increases, which is inconvenient. On the other hand, if the thickness of the third n-type layer is smaller than the thickness of the second n-type layer, the driving current cannot be sufficiently diffused, which disadvantageously reduces the light emitting area. The layer thickness of the second n-type layer is optimally 20 nm or more and 200 nm or less. The layer thickness of the second n-type layer can be easily controlled by adjusting the film formation time of the same layer.
[0015]
The electron concentration of the third n-type layer 105c exceeds the first and second electron concentrations, ensures good ohmic contact with the metal oxide window layer constituting the window layer 106, and reduces the drive current. A high electron concentration is used in order to diffuse planarly in the same layer 105c. The electron concentration of the third n-type layer 105c is at least about 1 × 10 ¹⁸ cm ⁻³ or more, preferably 5 × 10 ¹⁸ cm ⁻³ or more. When the carrier concentration is higher than 5 × 10 ¹⁹ cm ⁻³ , the flatness of the surface is disturbed, and it is difficult to stably obtain a metal oxide window layer having good ohmic contact. As an n-type impurity for forming such a high carrier concentration n-type (Al _X Ga _{1 -X} ) _0.5 In _0.5 P (0 ≦ X ≦ 1) layer, Se belonging to Group VI rather than Si can be used. Te is preferred.
[0016]
FIG. 2 illustrates an electron concentration distribution pattern of the n-type upper clad layer 105 including the first and third n-type layers 105a to 105c. In this case, in the upper clad layer 105, the electron concentration changes stepwise according to the electron concentration of each of the n-type layers 105a to 105c. FIG. 3 is an example showing another distribution state of the electron concentration of the upper clad layer 105, and is an example in which the electron concentration of each layer is changed relatively slowly as compared with FIG. The continuously varying the electron concentration in this manner, n-type _{(Al X Ga 1-X)} 0.5 In 0.5 P (0 ≦ X ≦ 1) amount of n-type dopant during formation of the layer over time It can be obtained by changing or raising or lowering the film formation temperature. The electron concentration can be measured by a general capacitance-voltage (CV) method using a Schottky junction type electrode.
[0017]
The third n-type layer 105c only needs to function as an ohmic contact layer for the n-type metal oxide window layer. For this reason, the layer thickness of the third n-type layer does not need to be so thick, and it is sufficient if it is 5 nm or more. A thin layer of about 2 to 3 nm or less is unlikely to be a continuous film that uniformly covers the entire surface of the second n-type layer. Therefore, good ohmic contact characteristics with the window layer are not brought about, and the driving current cannot be sufficiently diffused in the horizontal direction inside the third n-type layer 105c, which is disadvantageous. If the film thickness is greater than about 500 nm, the total amount of easily diffusible dopants contained in the layer will increase, increasing the chance that a large amount of dopant will penetrate into the light emitting layer, and impairing monochromaticity of light emission. Become.
[0018]
The first n-type layer 105a is also a layer for suppressing the amount of n-type impurities that enter the light-emitting layer from the third n-type layer 105c side, so that at least the third n-type layer 105c is formed. It is desirable to have a layer thickness exceeding. Considering that the general temperature when forming an n-type (Al _x Ga ₁ -x) _0.5 In _0.5 P (0 ≦ X ≦ 1) layer by the MO-VPE method is about 700 ° C. The thickness of one n-type layer 105a is preferably greater than about 0.5 μm. Further, the amount of n-type impurity diffused into the light emitting layer 104 can be reduced as the thickness of the first n-type layer 105a is increased.
[0019]
In the present invention, an n-type metal oxide window layer 106 is provided on the third n-type layer 105c. Both layers are preferably in contact with each other in order to simplify the element structure. As the metal oxide, for example, ITO, indium oxide, tin oxide, zinc oxide, magnesium oxide, and the like can be used, and it is particularly preferable to use n-type zinc oxide (chemical formula: ZnO). Unlike ITO, which is a mixture composed of indium oxide and tin oxide, zinc oxide, which is a single substance, has little change in resistance due to fluctuations in the mixing ratio of constituent materials, and resistance value reproducibility Has the advantage of being good. Zinc oxide has a high forbidden band width of about 3.35 eV at room temperature (see Teramoto, “Introduction to Semiconductor Devices” (Baifukan, first published on March 30, 1995), page 2.3, Table 2.3) has the _{(Al X Ga 1-X)} 0.5 in 0.5 P (0 ≦ X ≦ 1) high transmittance of about 90% with respect to emission of yellow-orange to a wavelength of, for example, it is emitted from the LED from 600nm and 630 nm.
[0020]
The zinc oxide crystal is a II-VI group compound semiconductor that exhibits n-type conduction in an undoped state. In particular, if a group III element is doped, a lower specific resistance n-type zinc oxide window layer is formed. Can be formed reliably. An n-type zinc oxide film doped with a Group III element such as aluminum (element symbol: Al), gallium (element symbol: Ga), or indium (element symbol: In) has a specific resistance of about 2 to 3 × 10 ^4. Ω · cm, and can be suitably used as a constituent material of the window layer. The electron concentration is preferably approximately 1 × 10 ²⁰ cm ⁻³ . For example, an n-type zinc oxide film to which both Al and Ga are added has a low specific resistance and is suitable for constituting a window layer. It is. The specific resistance of the zinc oxide crystal layer can be measured by a normal Hall effect measurement method or the like.
[0021]
A window layer 106 made of n-type zinc oxide can be formed on the surface of the third n-type layer 105c by a known physical deposition method such as a high-frequency sputtering method or a vacuum deposition method, a chemical deposition (CVD) method, or the like. . For example, it can be formed by sputtering using a molding material made of zinc oxide containing about 2 to 5% by weight of Al impurities as a target. It can also be formed by a laser ablation method in which the surface of such a target material is irradiated with laser light. The layer thickness of the zinc oxide window layer is desirably about 5 nm or more. If the thickness exceeds about 5 μm, the flatness of the surface of the zinc oxide layer is deteriorated, so that the in-plane emission intensity becomes non-uniform.
[0022]
【Example】
(Example 1)
Hereinafter, the present invention will be described in detail based on examples. FIG. 4 is a schematic plan view of the LED 20 according to this embodiment. FIG. 5 is a schematic diagram showing a cross-sectional structure along the broken line AA ′ of the LED 20 shown in FIG.
[0023]
On a zinc (Zn) -doped p-type (001) -GaAs single crystal substrate 301 ( hole concentration: 8 × 10 ¹⁸ cm ⁻³ ) inclined by 4 ° in the [110] direction, a Zn-doped p-type GaAs buffer layer 302, A lower clad layer 303 made of Zn-doped p-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P and a light-emitting layer 304 made of undoped (Al _0.2 Ga _0.8 ) _0.5 In _0.5 P mixed crystal were sequentially laminated. The buffer layer 302, the p-type lower cladding layer 303, and the light emitting layer 304 are made of trimethylaluminum ((CH ₃ ) ₃ Al), trimethyl gallium ((CH ₃ ) ₃ Ga), and trimethyl indium ((CH ₃ ) ₃ In) III. A film was formed at 720 ° C. by a reduced pressure MO-VPE method using a phosphine (PH ₃ ) as a group V constituent element source as a group constituent element raw material. Diethyl zinc ((C ₂ H ₅ ) ₂ Zn) was used as a Zn doping source. hole concentration of p-type lower cladding layer 303 is about 1 × 10 ¹⁸ cm ^-3, also the layer thickness was about 500 nm. The thickness of the light emitting layer 304 was about 150 nm, and the hole concentration was about 5 × 10 ¹⁶ cm ⁻³ .
[0024]
On the light emitting layer 304, an n-type upper cladding layer 305 was laminated. The upper clad layer 305 is formed by stacking first to third n-type layers 305a to 305c having different electron concentrations. The first n-type layer 305a is 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 about 1 μm and an electron concentration of 7 × 10 ¹⁷ cm ⁻³ . . The second n-type layer 305b 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 was composed of an n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P layer having a Se-doped layer thickness of 100 nm and an electron concentration of 2 × 10 ¹⁹ cm ⁻³ .
[0025]
A window layer 306 made of Al-doped ZnO was deposited on the surface of the upper cladding layer 305 by a general high-frequency sputtering method. The conductive transparent window layer 306 was composed of an n-type zinc oxide layer having a specific resistance at room temperature of about 3 × 10 ⁻⁴ Ω · cm. The layer thickness was about 200 nm. The general X-ray diffraction analysis showed that the orientation of zinc oxide forming the window layer 306 is <0001> direction (C axis) and polycrystalline.
[0026]
On the zinc oxide window layer 306, an Al circular electrode 307 having a diameter of about 110 μm was provided using a general photolithography technique. A p-type ohmic electrode 308 is provided on the entire back surface of the GaAs substrate 301 by vacuum deposition of a gold / zinc alloy (Au 98 wt% -Zn 2 wt% alloy) and then alloying (alloying) at 420 ° C. for 2 minutes. It was. Thereafter, the LED 30 was cut into individual chips each having a substantially square shape with a side of about 350 μm.
[0027]
When a current of 20 milliamperes (mA) was passed between the aluminum electrode 307 and the p-type ohmic electrode 308 in the forward direction, substantially uniform red-orange light emission was obtained from substantially the entire surface of the zinc oxide window layer 306. The emission wavelength measured by the spectroscope was about 620 nm. Further, the half width of the emission spectrum was about 17 nm, and light emission excellent in monochromaticity was obtained. The forward voltage (@ 20 mA) was about 2.1 volts (V). Further, the emission intensity reached about 48 milli candela (mcd).
[0028]
(Example 2)
In the present embodiment, the present invention will be described in detail by taking as an example the case of forming an (AlGa) InPLED having a Bragg reflective layer. FIG. 6 is a schematic cross-sectional view of the LED 40 according to the present embodiment.
[0029]
[110] direction inclined 10 °, Zn dough doped p-type (100) -GaAs substrate 401: a (hole concentration 3 × 10 ¹⁹ cm ^-3) on trimethylaluminum _{((CH 3) 3 Al)} , trimethyl Magnesium (Mg) -doped p-type GaAs buffer layer 402 is formed by a general reduced pressure MO-VPE method using gallium ((CH ₃ ) ₃ Ga) and trimethylindium ((CH ₃ ) ₃ In) as group III constituent elements. Were laminated. The layer thickness of the p-type GaAs buffer layer 402 was about 0.2 μm, and the hole concentration was about 3 × 10 ¹⁸ cm ⁻³ .
[0030]
Next, a Bragg reflective layer 409 was laminated on the buffer layer 402. The Bragg reflection layer 409 includes an Mg-doped n-type Al _0.45 Ga _0.55 As layer 409a with an Al composition ratio of _0.45 and an Mg-doped n-type Al _0.90 Ga _0.10 As layer 409b with an Al composition ratio of 0.90. It was composed of 5 layers. The layer thickness of the first Bragg reflection layer constituting layer 409a made of the Al _0.45 Ga _0.55 As layer is about 42 nm, and the layer thickness of the second Bragg reflection layer constituting layer 409b made of the Al _0.90 Ga _0.10 As layer is about It was 49 nm. The hole concentrations of the constituent layers 409a and 409b of the Bragg reflection layer 409 are both about 1 × 10 ¹⁸ cm ⁻³ .
[0031]
On the Bragg reflection layer 409, a lower cladding layer 403 made of p-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P doped with Mg was laminated. The thickness of the lower cladding layer 403 was about 0.8 μm, and the hole concentration was about 3 × 10 ¹⁸ cm ⁻³ . On the p-type lower cladding layer 403, a light emitting layer 404 made of an undoped (Al _0.2 Ga _0.8 ) _0.5 In _0.5 P mixed crystal was laminated. The layer thickness of the light emitting layer 404 was about 100 nm, and the electron concentration was about 8 × 10 ¹⁶ cm ⁻³ .
[0032]
On the light emitting layer 404, an upper clad layer 405 made of n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P was laminated. The upper clad layer 405 was composed of first, second and third n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P layers. The first n-type layer 405a disposed by bonding the light-emitting layer 404, an electron concentration of about 3 × 10 ¹⁸ cm ^-3, Si doped n-type to approximately 1.7μm layer thickness (Al _0.7 Ga _{0.3) It} was composed of _0.5 In _0.5 P. The second n-type layer 405b was made of n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P having a Si-doped layer thickness of about 80 nm and an electron concentration of about 2 × 10 ¹⁷ cm ⁻³ . The electron concentration of the first and second n-type layers 405a and 405b was obtained by continuously changing the addition flow rate of disilane (Si ₂ H ₆ ) as a Si doping source over time. The third n-type layer 405c is an n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P having an electron concentration of about 1 × 10 ¹⁹ cm ⁻³ and a layer thickness of about 100 nm doped with Se at a high concentration. Consists of.
[0033]
On the third n-type layer 405c, a solid molding material (pellet) made of zinc oxide containing 3% by weight of Al and 1.0% by weight of In is oxidized by an electron beam vacuum deposition method. A zinc window layer 406 was formed. The specific resistance of the n-type zinc oxide constituting the window layer 406 is estimated to be about 4 × 10 ⁻⁴ Ω · cm according to the Hall effect measurement method, and the electron concentration is estimated to be about 9 × 10 ¹⁹ cm ^−3. It was. The layer thickness was about 100 nm.
[0034]
In the same manner as described in Example 1, an Al electrode 407 and a p-type ohmic electrode 408 were formed to produce an LED 40. When a drive current of 20 mA was passed in the forward direction, red-orange light emission having a wavelength of about 620 nm was transmitted through almost the entire surface of the zinc oxide window layer 406 and emitted. Moreover, the half width (FWHM) of the emission spectrum was about 18 nm, and light emission excellent in monochromaticity was brought about. The forward voltage when the current was 20 mA was about 1.9V. The emission intensity reached about 90 mcd.
[0035]
【The invention's effect】
In an n-side-up type AlGaInP light emitting diode, if the n-type upper cladding layer is configured according to the present invention, a high-intensity light emitting diode can be provided with a simple laminated structure.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a cross-sectional structure of an upper clad layer having a layer structure according to the present invention.
FIG. 2 is a schematic diagram showing an example of a distribution state of electron concentration inside an upper clad layer.
FIG. 3 is a schematic diagram showing another distribution state of the electron concentration inside the upper clad layer.
4 is a schematic plan view of the LED described in Example 1. FIG.
5 is a schematic cross-sectional view taken along the broken line AA ′ of the LED shown in FIG. 4. FIG.
6 is a schematic plan view of an LED described in Example 2. FIG.
[Explanation of symbols]
20 AlGaInP LED
30 AlGaInP LED
40 AlGaInP LED
103 p-type lower clad layer 104 light-emitting layer 105 upper clad layer 105a first n-type layer 105b second n-type layer 105c third n-type layer 106 n-type zinc oxide window layer 107 metal electrode 205c third n-type Layer 206 n-type zinc oxide window layer 207 metal electrode 301 p-type GaAs single crystal substrate 302 p-type GaAs buffer layer 303 p-type lower cladding layer 304 light-emitting layer 305 upper cladding layer 305a first n-type layer 305b second n-type Layer 305c third n-type layer 306 n-type zinc oxide window layer 307 metal electrode 308 p-type ohmic electrode 401 p-type GaAs single crystal substrate 402 p-type GaAs buffer layer 403 p-type lower cladding layer 404 light-emitting layer 405 upper cladding layer 405a First n-type layer 405b Second n-type layer 405c Third n-type layer 406 n-type zinc oxide window layer 407 Metal electrode 40 p-type ohmic electrode 409 Bragg reflection layer 409a first Bragg reflector layer structure layer 409b second Bragg reflector layer structure layer

Claims (10)

On a p-type GaAs single crystal substrate, a p-type lower cladding layer represented by (Al _x Ga _1-x ) _Y In _1-YP (0 ≦ X ≦ 1, 0 ≦ Y ≦ 1), a light emitting layer, And the n-type upper cladding layer (including the case where the mixed crystal ratios X and Y are different between the respective layers) and the light emitting diode having the window layer made of metal oxide, the n-type upper cladding layer has a different electron concentration. Layer (including the case where the mixed crystal ratios X and Y are different among the three layers, and in order from the layer closer to the light emitting layer, the first n-type layer (the electron concentration is n1, the layer thickness is d1), the second an n-type layer (electron concentration is n2 and layer thickness is d2), and a third n-type layer (electron concentration is n3 and layer thickness is d3) are included. A light emitting diode characterized by n3>n1> n2 and a layer thickness of three layers of d1> d3 ≧ d2 .   2. The light emitting diode according to claim 1, wherein an In mixed crystal ratio (1-Y) of each of the p-type lower cladding layer, the light emitting layer, and the n-type upper cladding layer is 0.5.   The light emitting diode according to claim 1, wherein the window layer is in contact with the third n-type layer. Electron concentration of the second n-type ^{layer, 1 × 10 16 cm -3 ≦} n2 ≦ 5 × 10 17 cm be ^-3, characterized in claims 1 to 3 of the light-emitting diode according to any one . The light-emitting diode according to a second of the layer thickness of the n-type layer, any one of claims 1 to 4, characterized in that a 20nm ≦ d2 ≦ 200nm. Dopants of the first and second n-type layer is Si, the light emitting diode according to any one of claims 1 to 5, the dopant of the third n-type layer is characterized in that it is a Se or Te . Window layer, light-emitting diode according to any one of claims 1 to 6, characterized in that it has a n-type conductivity. The window layer is composed of at least one selected from indium tin oxide, indium oxide, tin oxide, zinc oxide, and magnesium oxide, The light emission according to any one of claims 1 to 7 , diode. The light emitting diode according to claim 8 , wherein the zinc oxide constituting the window layer includes any one of aluminum, gallium, and indium. hole concentration of p-type GaAs single crystal ^{substrate, 5 × 10 18 ~5 × 10} 19 light-emitting diode according to any one of claims 1 to 9, characterized in that in the range of ^{cm -3.}

Images