JP2007096162A - Semiconductor light-emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a semiconductor light-emitting device capable of preventing decrease in light-emitting output in time and increase in a driving voltage in addition to high luminance and low driving voltage. <P>SOLUTION: In the light-emitting device, a light-emitting portion consisting of at least an n-type cladding layer, an active layer and a p-type cladding layer is formed on a semiconductor substrate, and an As-based contact layer doped with a p-type dopant of 1×10<SP>19</SP>/cm<SP>3</SP>or more is formed on the upper part of the light-emitting portion, and a current dispersion layer consisting of a metal oxide material is formed on the upper part of the contact layer. The device has a buffer layer which includes P (phosphate) in the component of a group V element and is configured by an undoped group III/V semiconductor having H (hydrogen) concentration of 3×10<SP>17</SP>atoms/cm<SP>3</SP>, between the contact layer and the p-type cladding layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a semiconductor light emitting device, and more particularly to a high brightness semiconductor light emitting device using a transparent conductive film as a current spreading layer.

  Conventionally, light-emitting diodes (hereinafter abbreviated as LEDs), which are semiconductor light-emitting elements, have been able to grow GaN-based and AlGaInP-based high-quality crystals by the MOVPE (metal organic vapor phase epitaxy) method. Green, orange, yellow, and red high-brightness LEDs can be manufactured.

  However, in order to obtain high brightness, it is necessary to improve current dispersion characteristics so that current is uniformly injected into the LED chip surface. For example, in an AlGaInP-based LED element, the thickness of the current dispersion layer is 5 μm. It was necessary to increase the thickness to about 10 μm. For this reason, the raw material cost required for the growth of the current dispersion layer is increased, and the manufacturing cost of the LED element is inevitably increased, which hinders the production of an AlGaInP-based LED at a low cost.

  Therefore, ITO (Indium Tin Oxide) or ZnO (Zinc Oxide) is used as a current-dispersing film that has sufficient translucency and good electric current dispersion characteristics. A method used for the layer has been proposed (see Patent Document 1). A method for directly forming an ITO film on a p-type cladding layer has also been proposed (see Patent Documents 2 and 3).

Thus, if the ITO film can be used as the current spreading layer, the conventional method of thickening the semiconductor layer to about 5 μm to 10 μm is not required as the current spreading layer, and the corresponding epitaxial layer becomes unnecessary. Thus, it becomes possible to manufacture LED elements having high brightness and epitaxial wafers for LED elements at low cost.
JP-A-8-83927 US Reissue Patent No. 35665 Specification US Pat. No. 6,057,562

  However, when an ITO film is used for the window layer, a contact resistance is generated between the semiconductor layer and the ITO film which is a metal oxide, and there is a problem that the forward operation voltage becomes high. That is, the ITO film as the transparent conductive film (transparent electrode) is an n-type semiconductor, while the upper cladding layer in contact with the ITO film is a p-type semiconductor. Therefore, when a forward operating voltage is applied to the LED, a reverse bias state is established between the transparent conductive film (transparent electrode) and the p-type cladding layer, so that a current flows unless a large voltage is applied. Absent.

  As a solution to this, there is a method in which a thin high carrier concentration layer (contact layer) is provided so as to be in contact with the ITO film, and the LED is driven at a low voltage by a tunnel junction (for example, Patent Document 2).

  However, this contact layer is intended to be a tunnel junction and acts as an absorption layer for light emitted from the active layer. Therefore, the contact layer has a high carrier concentration and needs to be formed in a thin film. There was a problem that dopant diffusion was easily caused. In particular, due to the structure in which a contact layer having a high carrier concentration is formed on the p-type cladding layer, the distance between the contact layer and the active layer is short, so that diffusion is large. The problem of the diffusion of the p-type dopant in the contact layer causes the following two problems.

  The first adverse effect is a reduction in the output of the LED element. The p-type dopant diffused from the contact layer diffuses in the depth direction of the LED element and becomes a defect in the active layer when diffused to the active layer of the LED element. The defect becomes a non-radiative recombination component, and as a result, the output of the LED element decreases.

  A second adverse effect is that the drive voltage (forward operation voltage) of the LED element increases. Due to the diffusion of the p-type dopant, the substantial carrier concentration of the contact layer, which is a high carrier concentration layer of the thin film, is lowered, so that the above-described tunnel junction becomes difficult to achieve, and the tunnel voltage rises. As a result, the drive voltage of the LED element increases.

  Regarding the above problem, a buffer layer having a lower resistance than the p-type cladding layer, for example, an AlGaAs layer, is provided between the p-type cladding layer and the contact layer that is the high carrier concentration layer. There is a method of increasing the distance (Patent Document 3). Incidentally, this AlGaAs or AlAs layer is optically transparent with respect to the emission wavelength, and also has a crystal growth easier than that of a quaternary material such as AlGaInP, and also a lattice with an AlGaInP material that constitutes the light emitting portion. Conventionally, it has been generally used because the consistency is almost the same.

  However, the method of Patent Document 3 cannot solve the problem of easily causing dopant diffusion. As a cause, in order to lower the resistance of the buffer layer than that of the p-type cladding layer, diffusion is increased by adding many additives, and the material constituting the buffer layer is This is because when the semiconductor material is transparent to the emission wavelength using As as the group V element, for example, when an AlGaAs layer having a high Al mixed crystal ratio is used, diffusion becomes significant.

  The present inventors have also found that the cause of the dopant diffusion described above is that the H (hydrogen) concentration of the buffer layer or p-type cladding layer in contact with the contact layer is high. In other words, it has been found that the diffusion of the dopant becomes significant as the H concentration increases, leading to a decrease in output of the LED element and an increase in driving voltage.

  Accordingly, an object of the present invention is to provide a semiconductor light emitting device capable of solving the above-described problems and suppressing a decrease in light emission output with time and an increase in driving voltage in addition to high luminance and low driving voltage. It is to provide.

  In order to achieve the above object, the present invention is configured as follows.

In the semiconductor light emitting device according to the first aspect of the present invention, a light emitting portion including at least an n-type cladding layer, an active layer, and a p-type cladding layer is formed on a semiconductor substrate, and 1 × 10 ¹⁹ / cm above the light emitting portion. ^In a semiconductor light emitting device in which an As-based contact layer to which ^three or more p-type dopants are added is formed, and a current spreading layer made of a metal oxide material is formed on the contact layer, the contact layer and the p-type cladding Between the layers, the group V element is composed of an undoped III / V semiconductor containing P (phosphorus) as a component and an H (hydrogen) concentration of 3 × 10 ¹⁷ atoms / cm ³ or less. It has a buffer layer.

Representative examples of III / V semiconductors containing P (phosphorus) as a group V element component include AlInP, AlGaInP, and GaP. Further, if the H concentration is high, the diffusion of the p-type dopant increases, resulting in a decrease in light emission output and an increase in driving voltage. Therefore, the H (hydrogen) concentration of the buffer layer is set to 3 × 10 ¹⁷ atoms / cm ³ or less. .

  Note that expressions such as “undoped” and “no addition” used in this specification are not positively or intentionally added (doping), and impurities such as C (carbon) are naturally added to the crystal. It is not used in the sense of eliminating even the case where is inevitably mixed.

In the semiconductor light emitting device according to the second aspect of the present invention, a light emitting portion including at least an n-type cladding layer, an active layer, and a p-type cladding layer is formed on a semiconductor substrate, and 1 × 10 ¹⁹ / cm above the light emitting portion. ^In a semiconductor light emitting device in which an As-based contact layer to which ³ or more p-type dopants are added is formed, and a current spreading layer made of a metal oxide material is formed on the contact layer, in the p-type cladding layer, It has a buffer layer composed of an undoped III / V semiconductor in which P (phosphorus) is contained in the group V element component and the H (hydrogen) concentration is 3 × 10 ¹⁷ atoms / cm ³ or less. Features.

  According to a third aspect of the present invention, in the semiconductor light-emitting device according to the first or second aspect, the buffer layer is a crystal lattice-matched to the substrate, and has a higher resistance than the p-type cladding layer. / V group semiconductor.

  According to a fourth aspect of the present invention, in the semiconductor light emitting device according to the third aspect, the buffer layer is made of a III / V group semiconductor having an Al composition smaller than that of the p-type cladding layer.

  According to a fifth aspect of the present invention, in the semiconductor light emitting device according to any one of the first to fourth aspects, an undoped layer is provided between the active layer and the p-type cladding layer.

A sixth aspect of the present invention is the semiconductor light emitting device according to any one of the first to fifth aspects, wherein the buffer layer has a C (carbon) concentration of 5 × 10 ¹⁶ atoms / cm ³ or less.

The reason why the C concentration is lowered in addition to the H (hydrogen) concentration is that the diffusion of Zn from the contact layer also changes depending on the C concentration. That is, even if the C concentration is high, the diffusion of Zn increases, and the light emission output decreases and the drive voltage increases. From this viewpoint, the specific value of the C (carbon) concentration is preferably 5 × 10 ¹⁶ atoms / cm ³ or less.

  According to a seventh aspect of the present invention, in the semiconductor light emitting device according to any one of the first to sixth aspects, an undoped layer is provided between the n-type cladding layer and the active layer.

  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, between the n-type cladding layer and the active layer, an n-type conductive material having a lower concentration than the n-type cladding layer. An n-type low-concentration layer made of a semiconductor containing a sex-determining impurity is provided.

  According to a ninth aspect of the present invention, in the semiconductor light emitting device according to any one of the first to eighth aspects, the current spreading layer is made of ITO (indium tin oxide).

The invention of claim 10 is the semiconductor light-emitting device according to any one of claims 1 to 9, wherein the thickness of the current dispersion layer is a relational expression of d = A × λ _p / (4 × n) [wherein A is a constant (1 or 3), λ _p is a wavelength of wavelength (unit: nm), and n is a refractive index].

The invention of claim 11 is the semiconductor light emitting device according to any one of claims 1 to 10, wherein the dopant of the contact layer is Zn (zinc), and the carrier concentration is 1 × 10 ¹⁹ / cm ³ or more. And the composition is Al _x Ga _1-x As (where 0 ≦ X ≦ 0.4).

There is a limit to semiconductor materials that can stably realize a contact layer with a high carrier concentration of 1.0 × 10 ¹⁹ / cm ³ or more. As the semiconductor materials, Zn-doped Al _x Ga _1-x As (0 ≦ X ≦ 0.4) is optimal. However, since the AlGaAs is not transparent to the emission wavelength, it is necessary to form it with a thin film of about 30 nm or less.

The invention of claim 12 is the semiconductor light-emitting device according to any one of claims 2 to 11, wherein the dopant of the p-type cladding layer is Mg (magnesium), and the p-type cladding layer and the n-type cladding layer , And the active layer is composed of (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ X ≦ 1, 0.4 ≦ Y ≦ 0.6).

  Examples of the p-type dopant include Mg and Zn. Although Zn is widely used as a p-type dopant in AlGaInP-based compound semiconductors, it is known that the diffusion constant is relatively large and adverse effects due to thermal processes and the like occur. Therefore, when Zn is used as a dopant and the carrier concentration of the p-type cladding layer is increased, Zn diffuses into the active layer and the LD element characteristics deteriorate. Therefore, for the p-type cladding layer, it is advantageous to increase the carrier concentration by using Mg having a diffusion constant smaller than that of Zn as the p-type impurity.

The p-type cladding layer, the n-type cladding layer, and the active layer are (Al _x Ga _{1 -x} ) _y In _{1 -y} P (where 0 ≦ X ≦ 1, 0.4 ≦ Y ≦ 0.6). Preferably, it is configured. The reason for selecting these materials strongly depends on being optically transparent with respect to the wavelength of light emitted from the LED element among materials substantially lattice-matched to the GaAs substrate.

  According to a thirteenth aspect of the present invention, in the semiconductor light emitting device according to any one of the first to twelfth aspects, 10 pairs or more of two semiconductor layers having different refractive indexes are provided between the semiconductor substrate and the n-type cladding layer. A light reflecting layer made of a semiconductor multilayer film is provided.

A fourteenth aspect of the present invention is the semiconductor light emitting device according to any one of the first to thirteenth aspects, wherein the carrier concentration of the current dispersion layer is 8 × 10 ²⁰ / cm ³ or more.

  According to a fifteenth aspect of the present invention, in the semiconductor light emitting device according to any one of the first to fourteenth aspects, the active layer has a multiple quantum well structure or a strained multiple quantum well structure.

  A sixteenth aspect of the present invention is the semiconductor light emitting device according to any one of the first to fifteenth aspects, wherein a sum of film thicknesses of the p-type cladding layer and the buffer layer is not less than 1000 nm and not more than 3000 nm. The thickness of the clad layer is 200 nm or more and 1000 nm or less.

  According to a seventeenth aspect of the present invention, in the semiconductor light emitting device according to any one of the first to sixteenth aspects, the thickness of the contact layer is not less than 1 nm and not more than 30 nm.

  According to an eighteenth aspect of the present invention, in the semiconductor light emitting device according to any one of the first to seventeenth aspects, the buffer layer is made of AlInP or AlGaInP that is optically transparent to the emission wavelength.

According to a nineteenth aspect of the present invention, in the semiconductor light emitting device according to the thirteenth aspect, the light reflecting layer is (Al _x Ga _{1 -x} ) _y In _{1 -y} P (where 0 ≦ X ≦ 1, 0.4 ≦ Y ≦ 0.6) and Al _x Ga _1-x As (where 0 ≦ X ≦ 1).

  According to a twentieth aspect of the present invention, in the semiconductor light emitting device according to any one of the first to nineteenth aspects, a p-type layer is formed between the active layer and the p-type cladding layer at a lower concentration than the p-type cladding layer. A p-type low concentration layer made of a semiconductor containing a conductivity determining impurity is provided.

  According to a twenty-first aspect of the present invention, in the semiconductor light emitting device according to the fifth, seventh, eighth or twentieth aspect, the thickness of the undoped layer, the n-type low concentration layer or the p-type low concentration layer is 100 nm or less. It is characterized by that.

  The invention according to claim 22 is the semiconductor light emitting device according to any one of claims 1 to 21, wherein a buffer layer having n-type conductivity and made of the same material as the semiconductor substrate is provided on the semiconductor substrate. It is characterized by providing.

  According to a twenty-third aspect of the present invention, in the semiconductor light emitting device according to any one of the second to twenty-second aspects, a lattice mismatch rate between the buffer layer and a semiconductor layer formed below is within ± 0.3%. It is characterized by.

Here, the lattice mismatch rate is obtained by the formula: lattice mismatch rate = (a _{epitaxial layer−} a _substrate ) / a _substrate . However, the a _{Epitaxial layer} is that the lattice constant of the epitaxial layer, and a _Substrate, is that the lattice constant of the substrate.

  According to a twenty-fourth aspect of the present invention, in the semiconductor light emitting device according to any one of the first to twenty-third aspects, the buffer layer is GaP.

According to the present invention, a light emitting portion including at least an n-type cladding layer, an active layer, and a p-type cladding layer is formed on a semiconductor substrate, and a p-type dopant of 1 × 10 ¹⁹ / cm ³ or more is added to the upper portion of the light emitting portion. It is assumed that the semiconductor light-emitting element is formed by forming the As-based contact layer and forming a current spreading layer made of a metal oxide material on the contact layer. Specifically, the dopant of the p-type cladding layer is Mg, the dopant of the high carrier concentration thin film contact layer is Zn, ITO or other transparent conductive film is used for the current spreading layer, and the current is further increased. There is a semiconductor light emitting device provided with the high carrier concentration thin film contact layer so as to be in contact with the dispersion layer.

The gist of the present invention is that, in such a semiconductor light emitting device, P (phosphorus) is contained in the group V element component between the contact layer and the p-type cladding layer or in the p-type cladding layer, and H The object is to provide an undoped III / V group semiconductor layer having a (hydrogen) concentration of 3 × 10 ¹⁷ atoms / cm ³ or less as a buffer layer.

  Therefore, according to the present invention, it is possible to more effectively suppress the diffusion of the p-type dopant from the contact layer, and it is possible to produce an LED element having a high output and a low operating voltage, and a decrease in light emission output with time. In addition, a highly reliable LED element capable of suppressing an increase in driving voltage can be manufactured with high yield.

  Hereinafter, the present invention will be described based on illustrated embodiments.

In this example, additive-free AlGaInP is used for the buffer layer.
An epitaxial wafer for red LED having a structure shown in FIG. An epitaxial growth method, an epitaxial layer thickness, an epitaxial structure, an electrode formation method, and an LED element manufacturing method are as follows.

On the n-type GaAs substrate 1, an n-type (Si-doped) GaAs buffer layer 2 (thickness: 200 nm, carrier concentration: 1 × 10 ¹⁸ / cm ³ ) and a light reflection layer 3 were sequentially stacked and grown by the MOVPE method. The light reflection layer 3 is a 20-pair DBR mirror (distributed Bragg reflection layer) in which 20 AlAlP layers and 20 Al _0.5 Ga _0.5 As layers are alternately provided. The film thickness of the light reflecting layer 3 was λ _p / (4 × n). Here, the wavelength λ _p indicates the emission peak wavelength of the LED element. N is the refractive index of each semiconductor material constituting the light reflection layer. The carrier concentration of the light reflecting layer 3 was about 1 × 10 ¹⁸ / cm ³ .
Further, an n-type (Si-doped) (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layer 4 (film thickness 400 nm, carrier concentration 1 × 10 ¹⁸ / cm ³ ), undoped (Al _0.1 Ga) _0.9 ) _0.5 In _0.5 P active layer 5 (film thickness 600 nm), p-type (Mg doped) (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 6 (film thickness 400 nm, carrier concentration 5 × 10 ¹⁷ / cm ³ ) Then, the layers were sequentially grown by the MOVPE method.
Further, an additive-free (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P buffer layer 12 is formed on the p-type (Mg doped) (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layer 6 (also simply referred to as the p-type cladding layer 6). (Film thickness 600 nm), p-type (Zn-doped) Al _0.1 Ga _0.9 As contact layer 8 (film thickness 3 nm, carrier concentration 7 × 10 ¹⁹ / cm ³ ) was sequentially stacked and grown by the MOVPE method.

The additive-free (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P buffer layer 12 (also simply referred to as the additive-free buffer layer 12 or the buffer layer 12) contains P (phosphorus) as a V group element component, and is a semiconductor. The crystal is lattice-matched to the substrate 1 and is composed of an undoped group III / V semiconductor. The additive-free buffer layer 12 is specifically made of AlGaInP or AlInP that is optically transparent to the emission wavelength and lattice-matched to the substrate, and the thickness of the additive-free buffer layer 12 is p-type cladding. The layer 6 is formed so that the sum with the film thickness (usually 200 nm to 600 nm) is 1000 nm to 3000 nm, that is, the film thickness is 400 nm to 2800 nm. This means that the device can be prevented from being destroyed in the wire bonding process.

The p-type (Zn-doped) Al _0.1 Ga _0.9 As contact layer 8 (also simply referred to as p-type contact layer 8) is made of Al _x Ga _1-x As (where 0 ≦ X ≦ 0.4), and the film thickness is Zn as a p-type dopant is added at a high concentration of 1 × 10 ¹⁹ / cm ³ or more.

  The growth temperature in the MOVPE growth was 650 ° C. from the n-type GaAs buffer layer 2 to the additive-free AlGaInP buffer layer 12, and the p-type contact layer 8 was grown at 550 ° C. The other growth conditions were a growth pressure of about 6666 Pa (50 Torr), a growth rate of each layer of 0.3 to 1.0 nm / sec, and a V / III ratio of about 150.

However, the additive-free (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P buffer layer 12 has an appropriate V / III ratio of 200 for the purpose of reducing the H (hydrogen) concentration. By setting the V / III ratio to 200, the H (hydrogen) concentration of the additive-free (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P buffer layer 12 is reduced to 3 × 10 ¹⁷ atoms / cm ³ or less. Also, depending on the setting of the V / III ratio, C (carbon) may inevitably enter the buffer layer 12, but the C (carbon) concentration in the layer is also reduced to 5 × 10 ¹⁶ atoms / cm ³ or less. ing. The p / type contact layer 8 has a V / III ratio of 10. Incidentally, the V / III ratio mentioned here is the ratio (quotient) when the denominator is the number of moles of a group I raw material such as TMGa or TMAl, and the numerator is the number of moles of a group V raw material such as AsH ₃ or PH _3. Point to.

Examples of raw materials used in the MOVPE growth include organic metals such as trimethylgallium (TMGa), triethylgallium (TEGa), trimethylaluminum (TMAl), and trimethylindium (TMIn), arsine (AsH ₃ ), and phosphine (PH ₃ A hydride gas such as) was used. For example, disilane (Si ₂ H ₆ ) was used as an additive material for an n-type layer such as the n-type buffer layer 2 described above. Biscyclopentadienylmagnesium (Cp ₂ Mg) was used as an additive material for conductivity-determining impurities for p-type layers such as the p-type cladding layer 6. However, diethyl zinc (DEZn) was used only for the p-type contact layer 8.

In addition, hydrogen selenide (H ₂ Se), monosilane (SiH ₄ ), diethyl tellurium (DETe), dimethyl tellurium (DMTe) can also be used as an additive material for the conductivity determining impurity of the n-type layer. In addition, dimethyl zinc (DMZn) and diethyl zinc (DEZn) can also be used as a p-type additive material for the p-type cladding layer 6.

Further, after this LED epitaxial wafer was unloaded from the MOVPE apparatus, an ITO film 9 having a thickness of 80 nm was formed on the surface of the wafer, that is, on the surface side of the p-type contact layer 8. In this structure, the ITO film 9 becomes a current dispersion layer. The film thickness of the ITO film 9 which is a current dispersion layer is a relational expression of d = A × λ _P / (4 × n) [where A is a constant (1 or 3), and λ _P is an emission wavelength (unit: nm). , N is a refractive index] and is in a range of ± 30% of d obtained by The ITO film 9 is formed by vacuum deposition or sputtering, and has a carrier concentration of 8 × 10 ²⁰ / cm ³ or more immediately after the film formation.

The glass substrate for evaluation set in the same batch of ITO film deposition was taken out, cut into a size capable of Hall measurement, and the electrical characteristics of the ITO film 9 alone were evaluated. The carrier concentration was 1.1 × 10 ²¹ / cm ^3. The mobility was 16.7 cm ² / Vs, and the resistivity was 3.3 × 10 ⁻⁴ Ω · cm.

  Then, a surface electrode 10 having a diameter of 110 μm, which is a circular electrode, is vacuum-deposited in the form of a matrix on the upper surface of the epitaxial wafer by making full use of equipment used in general photolithography processes such as a resist and a mask aligner and a well-known method. Formed by the law. The lift-off method was used for electrode formation after the deposition. The surface electrode 10 was formed by depositing Ni (nickel) and Au (gold) in the order of 20 nm and 500 nm, respectively. Further, a back electrode 11 was formed on the entire bottom surface of the epitaxial wafer by the same vacuum deposition method. The back electrode 11 is formed by depositing AuGe (gold / germanium alloy), Ni (nickel), and Au (gold) in the order of 60 nm, 10 nm, and 500 nm, respectively, and then performing an alloy process that is alloying of the electrodes with nitrogen gas. It was performed by heating to 400 ° C. in an atmosphere and heat treating for 5 minutes.

  Thereafter, the LED epitaxial wafer with an electrode configured as described above was cut using a dicing apparatus so that the circular surface electrode 10 was positioned substantially at the center, thereby producing an LED bare chip having a chip size of 300 μm square. Further, the LED bare chip was mounted on a TO-18 stem (die bonding), and then wire bonding was performed on the mounted LED bare chip to produce an LED element.

  As a result of evaluating the initial characteristics of the LED element fabricated as described above, it is possible to obtain an LED element having excellent initial characteristics of a light emission output of 2.05 mW and an operating voltage of 1.85 V when energized with 20 mA (during evaluation). I was able to.

  Furthermore, as a result of driving the LED element at 50 mA in a normal humidity environment and performing a continuous energization test for 168 hours (1 week) as a result, the relative comparison value with the state before the test was an output of 102% (energization) The pre-emission output is set to 100% (hereinafter abbreviated as relative output), and the operating voltage is +0.004 V (about 0.2% increase).

In this manner, since the buffer layer 12 is not added and the H (hydrogen) concentration and the C concentration in the buffer layer 12 are reduced, the diffusion of Zn from the contact layer 8 is extremely effectively suppressed. Further, the buffer layer 12 does not use an As-based material transparent to the undoped (Al _0.1 Ga _0.9 ) _0.5 In _0.5 P active layer 5 (also simply referred to as the active layer 5), for example, an AlGaAs layer having a high Al mixed crystal ratio. By using AlGaInP or AlInP composed of P-based as the group V element, excellent initial characteristics and high reliability can be obtained. Further, by using an AlGaInP or AlInP-based material that lattice-matches the substrate without using a lattice-mismatched wide band gap material such as GaP that is the same P-based material, the initial operating voltage can be kept low. . Therefore, it is possible to obtain a semiconductor light emitting element capable of suppressing a decrease in light emission output with time and an increase in driving voltage when driving the semiconductor light emitting element.

Moreover, as a result of performing the SIMS analysis of the LED element in the state immediately after the LED element fabrication and the state after the LED element fabrication and the energization test under the above conditions, in the LED element of the first embodiment before and after the energization test, There was no appearance of Zn as the dopant of the p-type contact layer 8 in the active layer 5, and it was confirmed that the active layer 5 hardly diffused from the contact layer 8. In other words, by using the additive-free AlGaInP buffer layer 12 having a low H concentration, it was possible to suppress the dopant diffusion of the LED element.
Incidentally, the absolute value of the lattice mismatch rate between the AlGaInP buffer layer 12 and the semiconductor layer formed below is 0.3% or less.

FIG. 2 shows a modification of the first embodiment. This is based on the premise that the buffer layer 12 made of AlGaInP or AlInP-based material having no intentional dopant addition and having a low H (hydrogen) concentration is formed as described above and the p-type active layer 5. An AlGaInP undoped layer 13 is provided as a diffusion preventing layer between the clad layers 6, an n-type (Si-doped) (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 4 (also simply referred to as an n-type clad layer 4) and an active layer 5, an AlGaInP undoped layer 14 is provided as a diffusion preventing layer. Instead of these undoped layers, a low concentration layer having a low carrier concentration may be provided as a diffusion preventing layer.

In this example, additive-free AlGaInP is used for the buffer layer, and the additive-free buffer layer is sandwiched between cladding layers.
As Example 2, a red LED epitaxial wafer having a structure shown in FIG. The epitaxial growth method, the epitaxial layer thickness, the epitaxial layer structure, and the LED element manufacturing method were basically the same as those in Example 1.

However, in Example 2, the thickness of the p-type cladding layer 6 is set to 200 nm, and the additive-free (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P buffer layer 12 is provided thereon with a thickness of 600 nm. The p-type cladding layer 6 has a structure in which a layer having the same configuration as that of the p-type cladding layer 6 is provided to 200 nm.

At this time, the V / III ratio of the additive-free (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P buffer layer 12 is 200. By setting the V / III ratio to 200, the H (hydrogen) concentration of the additive-free (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P buffer layer 12 is reduced to 3 × 10 ¹⁷ atoms / cm ³ or less, and at the same time The C (carbon) concentration in the layer was also reduced to 5 × 10 ¹⁶ atoms / cm ³ or less.

  The LED characteristics with the above structure were a light emission output of 1.98 mW, an operating voltage of 1.86 V, and a relative output of 99%. For this reason, the LED element which has the outstanding initial characteristic was able to be obtained. In addition, the SIMS analysis result of the LED element in the state after conducting the energization test under the same conditions as in Example 1 confirmed that there was no diffusion of Zn into the active layer as in Example 1.

In this example, additive-free AlGaInP is used for the buffer layer, and an undoped layer or a low concentration layer is provided between the active layer and the cladding layer.
As Example 3, a red LED epitaxial wafer having a structure as shown in FIG. The epitaxial growth method, the epitaxial layer thickness, the epitaxial layer structure, and the LED element manufacturing method were basically the same as those in Example 1.

However, in Example 3, an (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P undoped layer 13 having a thickness of 75 nm was provided between the active layer 5 and the p-type cladding layer 6.

As a modification of Example 3, as shown in FIG. 5, an LED element in which an (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P undoped layer 14 a having a thickness of 75 nm is provided between the n-type cladding layer 4 and the active layer 5. Although not shown in the figure, an LED element provided with a 75 nm (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P low concentration layer (Si-doped, carrier concentration 2 × 10 ¹⁷ / cm ³ ) instead of the undoped layer 14a. And made each.

  The LED characteristics of the above three types of structures are a light emission output of 1.97 to 2.15 mW, an operating voltage of 1.85 to 1.888 V, a relative output of 101 to 105%, and an LED element having excellent initial characteristics is obtained. I was able to.

In this example, AlInP is used for the buffer layer and the p-type cladding layer.
As Example 4, an epitaxial wafer for red LED having a structure shown in FIG. The epitaxial growth method, the epitaxial layer thickness, the epitaxial layer structure, and the LED element manufacturing method were basically the same as those in Example 1. The difference from the first embodiment is as follows.

  In Example 4, an LED element using a p-type AlInP clad layer 15 made of AlInP and an additive-free AlInP buffer layer 16 instead of the p-type clad layer 6 and the additive-free buffer layer 12 having a low H concentration. Was made. The film thicknesses are 400 nm and 600 nm, respectively. As a modification of Example 4, an LED element using a p-type AlInP cladding layer 15 and an additive-free buffer layer 12 was also produced.

  As a result of evaluating the initial characteristics of the two types of LED elements thus fabricated, the LED characteristics when energized with 20 mA (during evaluation) were 1.96 mW and 2.11 mW, and the operating voltage was 1.88 V and 1 respectively. It was .87 V, and an LED element having excellent initial characteristics could be obtained.

  Furthermore, when the current supply test was conducted under the same conditions as in Example 1, the relative outputs of the two types of LED elements were 97% and 99%, respectively. As described above, with the configuration described in Example 4, an LED element having excellent initial characteristics could be obtained.

This is an example using a multiple quantum well (MQW) active layer.
As Example 5, a red LED epitaxial wafer having a structure as shown in FIG. The epitaxial growth method, the epitaxial layer thickness, the epitaxial layer structure, and the LED element manufacturing method were basically the same as those in Example 1. The difference from the first embodiment is as follows.

The fifth embodiment is different in that the MQW active layer 17 having a multiple quantum well (MQW) structure as the active layer 5 is used. In the multi-quantum well, the barrier layer is (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P (7.5 nm), and the well layer as the light emitting layer is Ga _0.5 In _0.5 P (5.5 nm). These pairs were used as one pair for a total of 40.5 pairs.

  As a modification of Example 5, an LED having a so-called strained multiple quantum well structure in which the balance of Ga and In in the well layer of the MQW active layer 17 was slightly changed (Ga decrease and In increase) was also manufactured.

  As a result of evaluating the initial characteristics of the two types of LED elements fabricated in this manner, the LED characteristics at the time of 20 mA energization (evaluation) are the light output 2.12 mW and 2.21 mW, and the operating voltages 1.84 V and 1.84 V, respectively. Thus, an LED element having excellent initial characteristics was obtained.

  Furthermore, when the current test was performed under the conditions described in Example 1, the relative outputs were 101% and 100%, respectively, and by using the configuration described in Example 5, the LED having excellent initial characteristics. An element was obtained.

In this example, GaP is used for the buffer layer.
As Example 6, an epitaxial wafer for red LED having a structure as shown in FIG. The epitaxial growth method, the epitaxial layer thickness, the epitaxial layer structure, and the LED element manufacturing method were basically the same as those in Example 1. The difference from the first embodiment is as follows.

In Example 6, an additive-free GaP layer (film thickness 600 nm) 18 was used as the buffer layer 12, and a p-type (Zn-doped) Al _0.1 Ga _0.9 As contact layer (film thickness 3 nm, carrier concentration 7 × 10 ¹⁹ / cm ^3). 8) were sequentially stacked and grown by the MOVPE method.

  Furthermore, the growth temperature in the MOVPE growth was 650 ° C. from the n-type GaAs buffer layer 2 to the p-type cladding layer 6, and the p-type contact layer 8 was grown at 550 ° C. The GaP buffer layer 18 was grown at a growth temperature of 680 ° C. and a V / III ratio of 50.

  As a result of evaluating the initial characteristics of the LED element fabricated in this way, it is possible to obtain an LED element having excellent initial characteristics with a light emission output of 2.18 mW and an operating voltage of 1.93 V when the 20 mA current is supplied (evaluation). I was able to.

  Furthermore, when the electricity supply test was done on the conditions as described in Example 1, the relative output was 95%.

  As described above, by using the additive-free GaP buffer layer 18, the initial operating voltage of the LED element is slightly increased and the reliability is slightly deteriorated, but an LED element excellent in terms of light emission output is obtained. I was able to. The increase in operating voltage depends on the use of GaP having a lattice mismatching material and a wide band gap as the buffer layer material. Moreover, although the reliability is slightly deteriorated, this also depends on the use of GaP for the same reason as described above.

The optimum conditions for obtaining a semiconductor light emitting device having an additive-free buffer layer of the present invention are as follows.
First, the contact layer 8 in contact with the ITO film 9 of the current spreading layer made of a metal oxide needs to be doped with a conductivity determining impurity at a very high concentration. Therefore, in the case of the contact layer 8 to which Zn (zinc) is added, the crystal material is preferably GaAs having an Al mixed crystal ratio of 0 to 0.4, or AlGaAs, and the carrier concentration is 1 × 10 ^19. / Cm ³ or more is preferred, and the higher the better. The ITO film 9 basically belongs to an n-type semiconductor material, and the LED element is generally manufactured by p-side up in many cases. For this reason, the LED element in which the ITO film 9 is applied to the current spreading layer has an n / p / n junction from the semiconductor substrate side, and a large potential barrier is generated at the interface between the ITO film 9 and the p-type semiconductor layer. Becomes an LED element having a very high operating voltage. In order to solve this problem, the contact layer 8 having a very high carrier concentration is required for the p-type semiconductor layer. The reason why the band gap of the contact layer 8 is narrow depends strongly on the fact that it is easier to increase the carrier.

Further, in conjunction with the increase in carrier density of the contact layer 8, the carrier concentration of the ITO film 9 in contact with the contact layer 8 is also important for reducing the tunnel voltage. For the same reason as the contact layer 8, it is preferably as high as possible. Specifically, it preferably has a carrier concentration of 8 × 10 ²⁰ / cm ³ or more.

Secondly, the thickness of the contact layer 8 is preferably in the range of 1 nm to 30 nm. This is because the contact layer 8 has a band gap that serves as an absorption layer for the light emitted from the active layer 5, so that the light emission output decreases as the film thickness increases.
Therefore, as can be seen from FIG. 9, the upper limit of the thickness of the contact layer 8 is preferably about 30 nm. Further, when the thickness of the contact layer 8 is less than 1 nm, tunnel junction between the ITO film 9 and the contact layer 8 becomes difficult this time, so the operating voltage is lowered and the operating voltage is stabilized. Becomes difficult. Therefore, the thickness of the contact layer 8 in contact with the ITO film 9 is preferably 1 nm to 30 nm.

Third, the thickness of the current dispersion layer made of a metal oxide is expressed by the following relational equation: d = A × λ _P / (4 × n) [where A is a constant (1 or 3), and λ _P is the emission wavelength ( (Unit: nm), n is a refractive index], and is preferably in the range of ± 30% of d determined by The ITO film 9 of the current spreading layer formed on the LED epitaxial wafer has a refractive index approximately in the middle between the semiconductor layer and the air layer, and functions optically as an antireflection film. Therefore, in order to improve the light extraction efficiency of the LED element and obtain an LED element with higher output, it is preferable to set the film thickness according to the above formula. However, as the thickness of the ITO film 9 increases, the transmittance tends to deteriorate. When the intrinsic transmittance of the ITO film 9 decreases, the ratio of the light emitted from the active layer 5 absorbed by the ITO film 9 increases, and as a result, the light emission output decreases. Further, as the thickness of the ITO film 9 increases, light interference in the layer increases, and the wavelength region with high light extraction efficiency becomes narrow. For these, an ITO film 9 is appropriately formed on the GaAs substrate 1, light is incident on the sample perpendicularly, and the result of measuring the spectrum of the reflected light at this time is shown in FIG.

  That is, for these reasons, the more preferable current distribution layer thickness d is in the above relational expression, and the constant A is preferably 1 or 3. Furthermore, the film thickness d of the ITO film 9 of the current dispersion layer formed on the LED epitaxial wafer may be within a range of ± 30% of the value obtained by the above relational expression. This is because the wavelength band having a low optical reflectance as the antireflection film, that is, the wavelength band having a high light extraction efficiency has a certain width. For example, as an antireflection film, the allowable value of the film thickness at which the reflectance is 15% or less when light is vertically incident on the LED epitaxial wafer on which the ITO film 9 is formed is the film thickness obtained from the above formula. It is in the range of ± 30% of d. When the film thickness d exceeds the range of ± 30%, the effect as an antireflection film is reduced, and the output of the LED element is lowered.

  Fourth, the thickness of the buffer layer 12 intervening between the contact layer 8 and the p-type cladding layer 6 is preferably 400 nm or more and 2800 nm or less. For example, when the p-type cladding layer 6 is 400 nm, the thickness of the buffer layer 12 is 600 nm to 2600 nm. The reason why the thickness of the buffer layer 12 is 400 nm or more is that if the distance from the active layer 5 to the surface electrode 10 is too short, the LED element is destroyed by ultrasonic vibration or the like in the wire bonding process when the LED element is manufactured. It is. On the contrary, the reason why the upper limit is set to 2800 nm or less is that the current dispersion characteristic of the LED element can be expected to have a sufficient effect by the ITO film 9 provided on the contact layer 8. Even if a thick buffer layer 12 having a thickness of about 10 μm is provided, since the current dispersion effect by the ITO film 9 described above is dominant, a dramatic improvement in output as an LED element cannot be expected. Rather, the cost for manufacturing the LED element increases, resulting in a demerit that the cost of the LED element is increased. Therefore, since the thickness of the p-type cladding layer 6 is usually 200 nm to 600 nm, the thickness of the buffer layer 12 is preferably in the range of about 400 nm to 2800 nm.

  In the contents described in the present invention, the composition of the buffer layer 12 and the p-type cladding layer 6 may be the same depending on the case. In this case, the distance from the upper end of the active layer 5 to the lower end of the contact layer 8 is It is preferable to be 1000 nm or more and 3000 nm or less.

  Fifth, if the film thickness of the undoped layers 13 and 14a in contact with the active layer 5 and the low-concentration layer is excessively large, the supply of carriers to the active layer 5 is deteriorated and the light emission output is reduced. Since the manufacturing cost increases, the thickness is preferably 100 nm or less.

  Sixth, the number of pairs of light reflecting layers 3 is preferably in the range of about 10 to 30 pairs. The reason for the lower limit is that it depends on the number of pairs necessary for the light reflecting layer 3 to have a sufficient reflectance. FIG. 11 shows the relationship between the number of stacked pairs of light reflecting layers and the vertical reflectance.

  Next, the grounds for the above upper limit of the number of pairs are as follows. As the light reflecting layer 3 is stacked infinitely thick, the reflectance does not increase and the light emission output of the LED element does not increase. As shown in FIG. 11, the reflectivity of the light reflecting layer 3 shows a saturation tendency almost completely from around 20 pairs, and is completely saturated around 30 pairs. Therefore, the number of pairs capable of obtaining an effective reflectance is required to be more than a certain level. Further, from the viewpoint of efficiently and inexpensively manufacturing the LED element and the LED epitaxial wafer, the light reflecting layer 3 The upper limit of the number of pairs is preferably 30 pairs or less.

As the preferred material of the light reflection of _{the, Al x Ga 1-x As} ( where, 0.4 ≦ X ≦ 1), or _{(Al x Ga 1-x)} y In 1-y P ( where, 0 ≦ X ≦ 1, 0.4 ≦ Y ≦ 0.6). The reason for selecting these materials strongly depends on being optically transparent with respect to the wavelength of light emitted from the LED element among materials substantially lattice-matched to the GaAs substrate 1. As is known, the DBR that is the light reflection layer 3 has a wider reflection wavelength band of light and a higher reflectance when the difference in refractive index between the two types of materials is larger. Accordingly, the material is preferably selected from the above materials.

  In the embodiment of the present invention, a red LED element having an emission wavelength of 630 nm is used. However, in other LED elements manufactured using the same AlGaInP-based material, for example, an LED element having an emission wavelength of 560 nm to 660 nm, the material of each layer The carrier concentration, in particular the window layer, has no changes. Therefore, even if the emission wavelength of the LED element is set to a wavelength band different from that of the present embodiment, the same effect can be obtained.

  In the embodiment of the present invention, the LED element structure is provided in which the n-type buffer layer 2 is provided between the n-type GaAs substrate 1 and the n-type cladding layer 4. Even if the structure in which the cladding layer 4 or the DBR layer 3 is laminated is adopted, the intended effect of the present invention can be obtained.

  In the embodiments of the present invention, the surface electrode 10 has been described as having a circular shape, but the intended effect of the present invention can be achieved even with other irregular shapes such as a square, rhombus, and polygon. Obtainable.

  In the embodiment of the present invention, only the example using GaAs as the semiconductor substrate has been given, but in addition to this, the epitaxial wafer for LED using Ge as a starting substrate, or the starting substrate as GaAs or Ge, The effect intended by the present invention can also be obtained in an LED epitaxial wafer that is removed later and uses a metal substrate having a thermal conductivity equal to or higher than that of Si or Si as an alternative free-standing substrate.

In the embodiment of the present invention, the p-type cladding layer 6 and the buffer layer 12 are a combination of AlInP and AlGaInP. However, these combinations may be any combination as long as it is a material transparent to the emission wavelength. However, the intended effect of this patent can be obtained.
[Comparative Example 1]

In this example, AlGaAs is used for the buffer layer.
As Comparative Example 1, a red LED epitaxial wafer having a structure shown in FIG. The epitaxial growth method, the epitaxial layer thickness, the epitaxial structure, the electrode formation method, and the LED device manufacturing method were basically the same as those in Example 1. The difference from the first embodiment is as follows.

In this comparative example 1, a p-type (Mg-doped) Al _0.8 Ga _0.2 As buffer layer 7 (film thickness 600 nm, carrier concentration 1 × 10 ¹⁸ / cm ³ ) was provided as a buffer layer on the p-type cladding layer 6. The p-type AlGaAs buffer layer 7 has a V / III ratio of 30. Further, dimethyl zinc (DMZn) and diethyl zinc (DEZn) were used as p-type additive raw materials for the p-type buffer layer 7.

  Next, the LED epitaxial wafer produced as described above is made into an element, and the process is the same as in the first embodiment.

  As a result of evaluating the initial characteristics of the LED element thus fabricated, characteristics of a light emission output of 1.61 mW and an operating voltage of 1.86 V when 20 mA was energized (during evaluation) were obtained.

  However, as a result of conducting a continuous energization test under the same conditions as in Example 1, the relative output as a relative comparison value with the state before the test was 63%.

Moreover, the SIMS analysis of the LED element of the state immediately after LED element preparation and the state after performing the said electricity test after LED element preparation was performed. As a result, it was confirmed that Zn as the dopant of the p-type contact layer 8 was already diffused and mixed in the active layer 5 before the energization in the LED element of Comparative Example 1 before the energization test. After the energization, it was confirmed that the diffusion of Zn further progressed and the amount of Zn mixed in the active layer 5 increased. The element life of the LED element shown in this comparative example 1, that is, the cause of the decrease in reliability is due to this dopant diffusion. Moreover, the cause of the low output of the LED element is also due to dopant diffusion.
[Comparative Example 2]

This is an example in which a contact layer and ITO are provided on a p-type cladding layer without using a buffer layer.
As Comparative Example 2, an epitaxial wafer for red LED having a structure as shown in FIG. The epitaxial growth method, the epitaxial layer thickness, the epitaxial layer structure, and the LED device manufacturing method were basically the same as those in Comparative Example 1. The difference from the first embodiment is as follows.

  In Comparative Example 2, the buffer layer was not provided on the p-type cladding layer 6, and the p-type contact layer 8 was provided directly on the p-type cladding layer 6.

  Next, the LED epitaxial wafer produced as described above is made into an element, and the process is the same as in the first embodiment.

  As a result of evaluating the initial characteristics of the LED element thus fabricated, an LED element having initial characteristics of a light emission output of 1.53 mW and an operating voltage of 1.87 V when energized with 20 mA (during evaluation) was obtained. Moreover, when the electricity supply test was done on the same conditions as the said Example 1, the relative output was 71%.

  Furthermore, as a result of conducting SIMS analysis of the LED element in the state immediately after the LED element fabrication and after the LED element fabrication and after conducting the energization test under the above-mentioned conditions, dopant diffusion occurs as in Comparative Example 1, and the activity It was confirmed that the amount of Zn mixed in the layer 5 increased.

1 is a cross-sectional structure diagram of an AlGaInP-based red LED according to Example 1 of the present invention. It is a cross-section figure of AlGaInP type | system | group red LED concerning the modification of Example 1 of this invention. It is a cross-section figure of AlGaInP type red LED concerning Example 2 of this invention. It is a cross-section figure of AlGaInP type red LED concerning Example 3 of this invention. It is a cross-section figure of AlGaInP type | system | group red LED concerning the modification of Example 3 of this invention. It is a cross-section figure of AlGaInP type red LED concerning Example 4 of this invention. It is a cross-section figure of AlGaInP type red LED concerning Example 5 of this invention. It is sectional drawing of AlGaInP type | system | group red LED concerning Example 6 of this invention. It is the figure which showed the film thickness of the contact layer, and the attenuation factor of the light emission output. It is the figure which showed the reflectance spectrum of the ITO film | membrane formed on the GaAs substrate. It is the figure which showed the relationship between the lamination | stacking pair number of a light reflection layer, and a vertical reflectance. 6 is a cross-sectional structure diagram of an AlGaInP red LED according to Comparative Example 1. FIG. 6 is a cross-sectional structure diagram of an AlGaInP red LED according to Comparative Example 2. FIG.

Explanation of symbols

1 n-type GaAs substrate 2 n-type GaAs buffer layer 3 light reflecting layer 4 n-type AlGaInP cladding layer (n-type cladding layer)
5 Undoped AlGaInP active layer (active layer)
6 p-type AlGaInP cladding layer (p-type cladding layer)
7 p-type buffer layer 8 p-type AlGaAs contact layer (p-type contact layer)
9 ITO film 10 Front electrode 11 Back electrode 12 Additive buffer layer 13 Undoped layer (diffusion prevention layer)
14, 14a, undoped layer (diffusion prevention layer)
15 p-type AlInP cladding layer 16 additive-free AlInP buffer layer 17 MQW active layer 18 additive-free GaP buffer layer

Claims (24)

An As-based material in which a light emitting part composed of at least an n-type cladding layer, an active layer, and a p-type cladding layer is formed on a semiconductor substrate, and a p-type dopant of 1 × 10 ¹⁹ / cm ³ or more is added to the upper part of the light emitting part. In a semiconductor light emitting device in which a contact layer is formed and a current spreading layer made of a metal oxide material is formed on the contact layer,
Between the contact layer and the p-type cladding layer, an undoped element containing P (phosphorus) as a group V element and having an H (hydrogen) concentration of 3 × 10 ¹⁷ atoms / cm ³ or less. A semiconductor light emitting device comprising a buffer layer made of a III / V semiconductor. An As-based material in which a light emitting part composed of at least an n-type cladding layer, an active layer, and a p-type cladding layer is formed on a semiconductor substrate, and a p-type dopant of 1 × 10 ¹⁹ / cm ³ or more is added to the upper part of the light emitting part. In a semiconductor light emitting device in which a contact layer is formed and a current spreading layer made of a metal oxide material is formed on the contact layer,
In the p-type cladding layer, an undoped III / V semiconductor in which P (phosphorus) is contained in the group V element component and the H (hydrogen) concentration is 3 × 10 ¹⁷ atoms / cm ³ or less. A semiconductor light emitting device comprising a buffer layer configured. In the semiconductor light-emitting device according to claim 1 or 2,
The semiconductor light emitting element, wherein the buffer layer is made of a III / V group semiconductor which is a crystal lattice-matched to the substrate and has a higher resistance than the p-type cladding layer. The semiconductor light-emitting device according to claim 3.
The semiconductor light emitting device, wherein the buffer layer is made of a III / V group semiconductor having an Al composition smaller than that of the p-type cladding layer. The semiconductor light-emitting device according to claim 1,
An undoped layer is provided between the active layer and the p-type cladding layer. The semiconductor light-emitting device according to claim 1,
The semiconductor light emitting device, wherein the buffer layer has a C (carbon) concentration of 5 × 10 ¹⁶ atoms / cm ³ or less. The semiconductor light-emitting device according to claim 1,
An undoped layer is provided between the n-type cladding layer and the active layer. The semiconductor light-emitting device according to claim 1,
An n-type low concentration layer made of a semiconductor containing an n-type conductivity determining impurity at a lower concentration than the n-type cladding layer is provided between the n-type cladding layer and the active layer. element. The semiconductor light-emitting device according to claim 1,
The semiconductor light-emitting device, wherein the current dispersion layer is made of ITO (indium tin oxide). The semiconductor light-emitting device according to claim 1,
The thickness of the current dispersion layer is d = A × λ _P / (4 × n) [where A is a constant (1 or 3), λ _P is an emission wavelength (unit: nm), and n is refraction. It is in the range of ± 30% of d determined by The semiconductor light-emitting device according to claim 1,
The contact layer has a dopant of Zn (zinc), a carrier concentration of 1 × 10 ¹⁹ / cm ³ or more, and a composition of Al _x Ga _1-x As (where 0 ≦ X ≦ 0.4). A semiconductor light emitting element characterized by the above. The semiconductor light-emitting device according to claim 2,
The dopant of the p-type cladding layer is Mg (magnesium), and the p-type cladding layer, the n-type cladding layer, and the active layer are (Al _x Ga _1-x ) _y In _1-y P (provided that 0 ≦ X ≦ 1, 0.4 ≦ Y ≦ 0.6). The semiconductor light-emitting device according to claim 1,
A semiconductor light emitting device comprising: a light reflecting layer comprising a semiconductor multilayer film in which 10 pairs or more of two semiconductor layers having different refractive indexes are provided between the semiconductor substrate and the n-type cladding layer. The semiconductor light-emitting device according to claim 1,
A semiconductor light emitting device, wherein the current spreading layer has a carrier concentration of 8 × 10 ²⁰ / cm ³ or more. The semiconductor light emitting device according to claim 1,
The active layer has a multiple quantum well structure or a strained multiple quantum well structure. The semiconductor light-emitting device according to claim 1,
A semiconductor light emitting element, wherein a sum of thicknesses of the p-type cladding layer and the buffer layer is 1000 nm or more and 3000 nm or less, and a thickness of the p-type cladding layer is 200 nm or more and 1000 nm or less. The semiconductor light-emitting device according to claim 1,
A semiconductor light-emitting element, wherein the contact layer has a thickness of 1 nm to 30 nm. The semiconductor light-emitting device according to claim 1,
The semiconductor light emitting element, wherein the buffer layer is made of AlInP or AlGaInP which is optically transparent with respect to an emission wavelength. The semiconductor light emitting device according to claim 13.
The light reflecting layer is (Al _x Ga _{1 -x} ) _y In _{1 -y} P (where 0 ≦ X ≦ 1, 0.4 ≦ Y ≦ 0.6) and Al _x Ga _1-x As (where 0 ≦ X ≦ 1). A semiconductor light emitting device characterized by being configured. The semiconductor light-emitting device according to claim 1,
A p-type low concentration layer made of a semiconductor containing a p-type conductivity determining impurity at a lower concentration than the p-type cladding layer is provided between the active layer and the p-type cladding layer. Light emitting element. The semiconductor light-emitting device according to claim 5, 7, 8, or 20,
The semiconductor light emitting device, wherein the undoped layer, the n-type low concentration layer or the p-type low concentration layer has a thickness of 100 nm or less. The semiconductor light-emitting device according to any one of claims 1 to 21,
A semiconductor light-emitting element, wherein a buffer layer having n-type conductivity and made of the same material as the semiconductor substrate is provided on the semiconductor substrate. The semiconductor light emitting device according to any one of claims 2 to 22,
A semiconductor light emitting device having a lattice mismatch ratio within ± 0.3% with a semiconductor layer formed under the buffer layer. 24. The semiconductor light emitting device according to claim 1, wherein
The semiconductor light emitting element, wherein the buffer layer is GaP.

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