JP2012069683A - Light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light emitting element having an electrode structure capable of spreading a current on an entire chip without increasing an optical absorption rate.SOLUTION: A light emitting element 1 has: a first surface as a light extraction surface; a second surface opposed to the first surface; a laminate structure 10 including a III-V compound semiconductor having a light-emitting layer 63; a reflective metal film 4 provided between a supporting substrate 3 and the second surface and reflecting emission lights of the light-emitting layer 63 toward the first surface; a plurality of first electrodes 70 provided on one part of the first surface and electrically conducted with the laminate structure 10; a transparent conductive film 71 provided on the first surface and electrically conducted with the first electrode 70; and an electrode pad 9 provided on the transparent conductive film 71.

Description

  The present invention relates to a light emitting element.

  Conventionally, as shown in FIG. 6B, a light emitting element 1C employing a structure in which a metal reflection film is sandwiched between an active layer and a Si substrate is known. In manufacturing such a light emitting element 1C, since an organic metal raw material containing a rare metal is used as a raw material in semiconductor epitaxy growth, the raw material cost becomes high. Therefore, it is preferable in terms of manufacturing cost to make the semiconductor crystal (laminated structure 10) thin.

  However, if the semiconductor layer (laminated structure 10) is made thin, the effect of current dispersion in the semiconductor layer is reduced, and it becomes difficult to uniformly inject current over the entire surface of the active layer 63. Therefore, as shown in FIG. 6A, by distributing the distribution electrode 90C from the electrode pad 9C to the chip surface, current can be uniformly injected into the entire laminated structure 10, and the maximum reliability can be obtained. A light emitting element having a high applied current value is realized. In addition, the forward voltage at the time of driving can be reduced and the efficiency can be effectively increased by flowing the current uniformly in the chip surface.

However, the active layer 63 is a relatively small light-emitting element having a predetermined size, for example, 150,000 μm ² or less, and, for example, a light-emitting element designed for a drive current of DC 100 mA or less emits light in the active layer 63. When the extracted light is extracted outside the chip, the distribution electrode 90C absorbs the light, so that there is a problem that the light extraction efficiency is reduced.

  In order to solve such a problem, a light-emitting element using a transparent conductive film has been devised (for example, see Patent Document 1). The light-emitting element described in Patent Document 1 spreads current over the entire stacked structure with a transparent conductive film and does not absorb light emitted from the active layer, so that the light extraction efficiency of the light-emitting element can be improved.

JP 2002-329889 A

  However, in the light emitting device described in Patent Document 1, it is necessary to increase the film thickness of the transparent electrode in order to spread the current over the entire laminated structure, and in order not to increase light absorption by the transparent electrode, the film thickness of the transparent electrode must be increased. Since it must be reduced, there is a problem that it is structurally impossible to broaden the current and not to increase the light absorption rate.

  Accordingly, an object of the present invention is to provide a light-emitting element having an electrode structure that can spread current over the entire chip without increasing the light absorption rate.

In order to solve the above problems, the present invention provides a support substrate, a first surface as a light extraction surface, a second surface opposite to the first surface, the first surface, and the A laminated structure made of a III-V group compound semiconductor having a light emitting layer between the second surface and the light emitted from the light emitting layer provided between the support substrate and the second surface; A reflective metal film reflecting to the surface side of the transparent metal film, a transparent insulating film provided between the interface of the reflective metal film and the semiconductor layer, and the second metal film penetrating through a part of the transparent insulating film. A second electrode that conducts electricity between the surface and the reflective metal film, a plurality of first electrodes that are provided on a part of the first surface to conduct electricity with the laminated structure, and the first electrode that is provided on the first surface. A transparent conductive film electrically conductive with the electrode, and an electrode pad provided on the transparent conductive film, and in plan view, The average value of the distance between one electrode and the second electrode at the shortest position with respect to the first electrode is 5 μm or more and 50 μm or less, and 70% of the distance is within ± 20 μm of the average value, A light emitting element in which the shortest distance between the first electrode and the second electrode is 10 μm or more, and the laminated structure has an area of the light emitting layer of 150,000 μm ² or less.

  In the light emitting device, it is preferable that the first electrode is disposed outside a region where the pad electrode is provided on the first surface in a plan view.

  In the light-emitting element, it is preferable that the second electrode is disposed outside the region where the region on which the first electrode is provided is projected on the first surface in plan view.

  In the light-emitting element, it is preferable that the second electrode is disposed outside the region where the electrode pad is provided on the first surface in a plan view.

  In the above light emitting device, it is preferable that the second electrode is disposed so that the shortest distance from each of the first electrodes is substantially equal in plan view.

  In the light-emitting element, it is preferable that the stacked structure has an uneven shape on the surface of the first surface.

  According to the light emitting device of the present invention, the current can be spread over the entire chip without increasing the light absorption rate.

FIG. 1A is a plan view for explaining the structure of a light-emitting element according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along the line AA in FIG. . FIG. 2A is a schematic cross-sectional view for explaining a manufacturing process for the light-emitting element according to the embodiment of the present invention. FIG. 2B is a schematic cross-sectional view for explaining a manufacturing process for the light-emitting element according to the embodiment of the present invention. FIG. 2C is a schematic cross-sectional view for explaining a manufacturing process for the light-emitting element according to the embodiment of the present invention. FIG. 2D is a schematic cross-sectional view for explaining a manufacturing process for the light-emitting element according to the embodiment of the present invention. FIG. 2E is a schematic cross-sectional view for explaining a manufacturing process for the light-emitting element according to the embodiment of the present invention. FIG. 2F is a schematic cross-sectional view for explaining a manufacturing process for the light-emitting element according to the embodiment of the present invention. FIG. 3 is a graph for explaining the relationship between the Al composition x and the contact resistance of the light emitting device according to the embodiment of the present invention. FIG. 4A is a graph for explaining the relationship between the area of the electrode pad of the light emitting element and the light emission output according to Example 1 of the present invention. FIG. 4B is a graph for explaining the relationship between the area of the electrode pad and the forward voltage of the light emitting device according to Example 1 of the invention. FIG. 4C is a graph for explaining the relationship between the area of the electrode pad and the energy efficiency of the light emitting device according to Example 1 of the invention. FIG. 5A is a graph for explaining the relationship between the total area of the first electrodes and the light emission output of the light emitting device according to Example 2 of the present invention. FIG. 5B is a graph for explaining the relationship between the total area of the first electrodes and the forward voltage of the light emitting device according to Example 2 of the invention. FIG. 5B is a graph for explaining the relationship between the total area of the first electrodes and the energy efficiency of the light emitting device according to Example 2 of the present invention. FIG. 6A is a schematic plan view for explaining the structure of a conventional light emitting device, and FIG. 6B is a schematic cross-sectional view taken along the line BB in FIG. 6A.

[Summary of embodiment]
A support substrate, a first surface as a light extraction surface, a second surface facing the first surface, and a light emitting layer between the first surface and the second surface III A laminated structure made of a -V group compound semiconductor, a reflective metal film provided between the support substrate and the second surface and reflecting the light emitted from the light emitting layer toward the first surface, and the reflective metal A transparent insulating film provided between the interface of the film and the semiconductor layer; and a second electrode that penetrates part of the transparent insulating film and that conducts the second surface and the reflective metal film; A plurality of first electrodes provided on a part of the first surface and electrically conductive with the laminated structure; a transparent conductive film provided on the first surface and electrically conductive with the first electrode; and An electrode pad provided on the first electrode, and is in the shortest position with respect to the first electrode and the first electrode in plan view The average distance between the two electrodes is 5 μm or more and 50 μm or less, 70% of the distance is within ± 20 μm of the average value, and the shortest distance between the pad electrode and the first electrode or the second electrode is 10 μm. As described above, the stacked structure provides a light-emitting element in which the area of the light-emitting layer is 150,000 μm ² or less.

[Embodiment]
FIG. 1A is a schematic plan view for explaining the structure of a light-emitting element according to an embodiment of the present invention, and FIG. 1B is a schematic cross-sectional view taken along the line AA in FIG. It is.

  The light emitting element 1 electrically connects the reflective metal film 4 that reflects the light emitted toward the support substrate 3 side to the active layer 63 side, the reflective metal film 4 and the P-type contact layer 60 on the support substrate 3 made of Si or the like. Connected second electrode 50, transparent insulating film 51 that transmits emitted light, P-type contact layer 60, P-type cladding layer 61, active layer 63 that emits light, and surface for improving light extraction efficiency The N-type cladding layer 64 having a concavo-convex shape, an N-type contact layer 65, a plurality of first electrodes 70 formed on the N-type contact layer 65, and the surfaces of the N-type cladding layer 64 and the first electrode 70 are covered. The transparent conductive film 71 formed by covering the surface and side surfaces of the transparent conductive film 71, the side surfaces of the N-type cladding layer 64, the side surfaces of the active layer 63, and the side surfaces of the P-type cladding layer 61. And an electrode pad 9 which is an N-side electrode There are laminated in this order, and a back electrode 2 is a P-side electrode on the back surface of the supporting substrate 3.

  The reflective metal film 4 is preferably a metal film having a reflectance of 80% or more with respect to the wavelength of the emitted light. For example, for light in the red wavelength band, it is preferably made of either Au, Ag, Al, or an alloy thereof. For light in the blue wavelength band, Ag, Al, or alloys thereof are preferred.

The transparent insulating film 51 is transparent to the emitted light, and is sandwiched between the semiconductor layers 60 to 65 (hereinafter referred to as “laminated structure 10”) and the reflective metal film 4. The film thickness of the transparent insulating film 51 is preferably (2 × λ) / (4 × n) or more when the emission wavelength λ and the refractive index of the transparent dielectric layer are n. Specifically, the transparent dielectric layer is made of SiO ₂ or SiN.

The transparent conductive film 71 functions as a role of spreading current in the plane of the light-emitting element 1, and thus has a resistivity of at least 1 × 10 ⁻³ Ω · cm and a film thickness of at least 50 nm. preferable.

  Further, the transparent conductive film 71 is formed of. In order to spread the current in the plane of the light emitting element 1, it is necessary on the light extraction surface side, but if it is formed on the side surface portion of the active layer 63, it is not formed because it causes PN junction leakage.

  Moreover, the laminated structure 10 of this Embodiment is comparatively thin, for example, is comprised by the thickness of 1-6 micrometers. That is, the distance between the surface of the N-type contact layer 65 and the active layer 63 is small. Therefore, when the chip of the light emitting element 1 is mechanically picked up, a PN junction leak is likely to occur due to damage due to contact with the side surface of the light emitting element 1 and so on the side surface of the light emitting element 1 (side surface of the active layer 63). In order to protect from this mechanical damage, it is preferable to form the transparent insulating film 8.

  In the light emitting element 1 of the present embodiment, light is emitted from the active layer 63 between the first electrode 70 and the second electrode 50 to the first electrode 70 side or the second electrode 50 side. Therefore, in order to increase the light extraction efficiency, it is important not to provide the second electrode 50 at a position overlapping the first electrode 70 in a plan view, that is, below the first electrode 70 in a cross-sectional view. It is also important not to provide the first electrode 70 and the second electrode 50 below the electrode pad 9 in order to reduce the light absorption effect of the electrode pad 9 that tends to act as a light absorption factor in the entire light emitting element 1. In addition, it is preferable that the distance between the first electrode 70 and the second electrode 50 that are the shortest distance from the edge of the electrode pad 9 and the edge of the pad 9 in plan view is 10 μm or more apart.

The electrode pad 9 for current injection is preferably of a size that allows wire bonding and that does not significantly affect the absorption factor of light emitted from the active layer 63 as described above. Area of the electrode pads 9, specifically, preferably 12000Myuemu ² or less there is 3500 ² or more in plan view. The upper limit was set to 12000 μm ² because it was found that the light extraction efficiency declined when the size was made larger than this.

The area of the first electrode 70 is determined such that the resistance value estimated from the contact resistance with the laminated structure 10 does not exceed a predetermined value, but the smaller the better. Further, the light extraction efficiency of the light emitting element 1 is not affected as a cause of absorbing the light emitted from the active layer 63. Specifically, the first electrode is preferably formed in a circular shape, for example, and the area thereof is preferably 1 to 100 μm ² or less. The first electrode 70 is preferably as small as possible, but if it is too small, the contact resistance with the contact layer increases and the forward voltage increases. Therefore, it is preferable to use a semiconductor layer made of Al _x Ga _1-x As (where 0 ≦ x ≦ 0.3) as the N-type contact layer 65 of the first electrode 70 so that the contact resistance does not increase. Further, it has been found that if the sizes of the first electrodes 70 are each 1 μm ² or more and the total area can be managed, an increase in the forward voltage can be suppressed.

  FIG. 3 is a graph for explaining the relationship between the Al composition x and the contact resistance of the light emitting device according to the embodiment of the present invention.

Relationship of the contact resistance [rho _c and Al composition, it can be seen that as shown in FIG. 3, the contact resistance with Al composition x = 0.3 or less is sufficiently small.

  If the distance between the first electrode 70 and the second electrode 50 is not uniform, the current injected in the active layer 63 is biased. Therefore, when the shortest distance between the first electrode 70 and the second electrode 50 is D, it is preferable that the shortest distances D are uniform, that is, the standard deviation is small, and at least 70% of the shortest distance D is The average value of the shortest distance D is preferably within ± 20 μm. Further, since the light emission of the active layer 63 occurs between the first electrode 70 and the second electrode 50, if the distance between the first electrode 70 and the second electrode 50 is small, the light emission is transmitted to the first electrode 70 or the second electrode 50. It becomes easy to be absorbed. Further, if the distance is large, the resistance of the laminated structure 10 contributes to the increase of the forward voltage, which is a problem. Therefore, the distance between the two electrodes is preferably in the range of 5 μm or more and 50 μm or less.

(Manufacturing process of light-emitting element 1)
2A to 2F are schematic cross-sectional views for explaining a manufacturing process of the light-emitting element according to the embodiment of the present invention.

  First, a GaN-based or AlGaInP-based high-quality crystal is grown on a GaAs substrate 67 by the MOVPE method, and as shown in FIG. 2A, a P-type contact layer 60, a P-type cladding layer 61, an active layer 63, an N-type cladding. The stacked structure 10 including the layer 64 and the N-type contact layer 65 and the etching stop layer 66 are formed. For example, the stacked structure 10 emits red light having a wavelength of about 630 nm.

  An epitaxial growth method, an epitaxial layer thickness, an epitaxial structure, an electrode formation method, and an LED element manufacturing method are as follows.

First, an etching stop layer 66 made of undoped (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P and an N type (Si-doped) GaAs N film are formed on an N-type GaAs substrate 67 by the MOVPE method. Type contact layer 65, N type (Si doped) (Al _0.7 Ga _0.3 ) _{0.5 In 0.5} clad layer 64 made of _{0.5 In 0.5} P, undoped (Al _0.1 Ga _0.9 ) _0. Active layer 63 made of ₅ In _0.5 P, P-type (Mg doped) (Al _0.7 Ga _0.3 ) P-type clad layer 61 made of _0.5 In _0.5 P, P-type (Mg doped) A P-type contact layer 60 made of GaP is sequentially stacked and grown.

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

Examples of raw materials used in the MOVPE growth include trimethylgallium (TMGa), organic metals such as triethylgallium (TEGa), trimethylaluminum (TMAl), and trimethylindium (TMIn), arsine (AsH ₃ ), and phosphine (PH ₃ ). A hydride gas such as can be used. Disilane (Si ₂ H ₆ ) can be used as an additive material for the N-type semiconductor layer. Biscyclopentadienyl magnesium (Cp ₂ Mg) can be used as an additive material for the conductivity type determining impurity of the P-type semiconductor layer.

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

Then, after unloading the epitaxial wafer including the stacked structure 10 from the MOCVD apparatus, as shown in FIG. 2B, a SiO ₂ film by a plasma -CVD apparatus P-type GaP surface. Next, using a general photolithography technique such as a resist or a mask aligner, an opening is formed in the SiO ₂ with a hydrofluoric acid etching solution. Next, a single ohmic contact junction is formed as the second electrode 50 in the opening by vacuum deposition. An AuZn (gold / zinc) alloy is used as the ohmic contact junction. In addition, the ohmic contact bonding portion is disposed so as to be in a region other than the region directly below the electrode pad 9 to be formed later in plan view.

  Next, as shown in FIG. 2C, Al, Ti, and Au were sequentially deposited on the epitaxial wafer with an ohmic contact junction as shown in FIG. 2C. Al is a reflective film, Ti is a diffusion barrier layer, and Au is a bonding layer.

  Further, Ti, Pt, and Au are vapor-deposited in this order on the surface of the conductive Si substrate 3 prepared as a support substrate, thereby forming the metal adhesion layer 41. Ti is an ohmic contact metal, Pt is a diffusion barrier layer, and Au is a bonding layer.

The ohmic contact junction and the epitaxial wafer with the reflective metal layer 40 produced as described above are bonded to the metal adhesion layer 41 on the Si substrate surface. Specifically, bonding is performed by holding at a temperature of 350 ° C. for 30 minutes under a pressure of 0.01 Torr and a load of 30 kgf / cm ² .

Next, as shown in FIG. 2D, the GaAs substrate 67 of the epitaxial wafer bonded to the Si substrate 3 is removed by etching with a mixed solution of ammonia water and hydrogen peroxide solution, and undoped (Al _0.7 Ga _0.3 ). _{After the} etching stop layer 66 made of _0.5 In _0.5 P is exposed, the etching stop layer 66 is further removed with hydrochloric acid to expose the N-type contact layer 65.

  Next, the first electrode 70 is formed on the surface of the N-type contact layer 65 by vacuum deposition using a general photolithography technique such as a resist or a mask aligner. First, as shown in FIG. 2E, AuGe (gold / germanium alloy), Ti, and Au to be the first electrode 70 are sequentially deposited on the entire surface of the N-type contact layer.

  Next, as shown in FIG. 2F, after the formation of the metal film to be the first electrode 70, the first electrode 70 is applied only to a predetermined region using an etching solution made of a mixed solution of sulfuric acid, hydrogen peroxide solution, and water. The N-type contact layer 65 in a region other than the first electrode 70 is removed by etching, and the N-type cladding layer 64 is exposed by selective etching. Further, patterning with a period of 1.0 μm to 3.0 μm is performed on the N-type cladding layer 64 serving as a light extraction surface by using a photolithography technique, and an uneven shape is formed on the surface of the N-type cladding layer 64 by wet etching.

  Next, a transparent conductive film 71 made of ITO covering the first electrode 70 and the N-type cladding layer 64 is formed by a sputtering apparatus. An ITO raw material target having a Sn concentration of 5% in weight percent concentration is used. The sputtering apparatus is an RF magnetron sputtering apparatus, and the film is formed with an RF input power of 50 W, no introduction of oxygen gas, a chamber pressure of 0.5 Pa, and a film formation time of 30 minutes. The thickness of the ITO film obtained at this time can be evaluated by spectroscopic ellipsometry of the Si dummy substrate sample put in the simultaneous batch. In this embodiment, the ITO film is formed to have a thickness of 80 nm and a refractive index of 1.98.

Thereafter, in order to separate the elements from each other, the ITO film between the elements is removed, and then the surface to the GaP contact layer are removed by a wet etching method. Further, a SiO ₂ film is formed as a chip protective film on the upper surface portion of the chip and the side surface portion of the chip with a plasma CVD apparatus, and the SiO ₂ protective film on the surface electrode portion is opened using a photolithography technique and an etching technique.

  Also, after forming a back electrode made of Ti and Au on the back surface of the Si substrate by vacuum deposition, the alloying process, which is electrode alloying, is heated to 400 ° C. in a nitrogen gas atmosphere and heat-treated for 5 minutes. It was done in. Further, two electrode pads 9 made of Ti and Au are formed on the two surface electrodes for wire bonding by a photolithography technique and a vacuum evaporation method.

  The LED epitaxial wafer having the electrode formed thereon was cut by using a dicing apparatus, and the LED bare chip having a chip size of 250 μm square was fabricated. Further, the LED bare chip is mounted on a TO-18 stem (die bonding), and then wire bonding is performed on the mounted LED bare chip to produce an LED element.

  The electrode pad 9 of the surface electrode is circular with a diameter of 100 μm. In addition, the surface electrode (first electrode 70) for taking electrical conduction between the ITO transparent conductive film 71 and the laminated structure 10 is a circle having a diameter of 5 μm. The distance between the first electrode 70 and the interface electrode (second electrode 50) for conduction between the laminated structure 10 and the reflective metal film 4 is set to a constant value as shown in FIG. The distance in the thickness direction of 1 is 12 μm.

  The light emitting device 1 was molded with an epoxy resin, and the characteristics as an LED when energized with 20 mA were the light emission output, the forward voltage was 19.0 mW, 2.01 V, and the energy efficiency was 47.3%. .

(Effect of embodiment)
Compared with the conventional light emitting device shown in FIG. 6, the surface output area, which is a light absorption factor, that is, the area of the first electrode 70 is greatly reduced, so that the light emission output is greatly improved. In addition, since the transparent conductive film 71 was designed so that the current of the laminated structure 10 was uniformly distributed, the forward voltage of the laminated structure 10 was successfully reduced.

  Further, in the structure of the conventional light emitting element, the light output cannot be increased unless the distance between the first electrode and the second electrode is increased in order to reduce the influence of light absorption of the surface electrode. However, when the distance between the first electrode and the second electrode is increased, the resistance component of the semiconductor layer is increased, and there is a limit due to the increase of the forward voltage. However, in this patent, by reducing the area of the first electrode in a dot shape one by one, even if the distance between the first electrode and the second electrode is reduced, the influence of light absorption is considerably small, and the high light emission output And a low forward voltage can be achieved simultaneously. As a result, energy efficiency has been significantly improved.

  200 μm square and 330 μm square light emitting elements having the structure of the light emitting element described in the embodiment were formed.

  In Example 1, the light emitting device 1 was manufactured by changing the area of the electrode pad 9. At this time, the surface electrode (first electrode 70) had a diameter of 5 μm, and the distance between the first electrode 70 and the second electrode 50 in the thickness direction of the light-emitting element 1 was set to 12 μm.

  Further, the structure of the light-emitting element 1 shown in FIG. 1 was manufactured by changing the number of pairs of the first electrode 70 and the second electrode 50 in accordance with each shape parameter.

When the area of the electrode pad 9 is 3500 μm ² or less, the yield of wire bonding decreases, so that the electrode pad 9 is made 3500 μm ² or more.

  4A to 4C show the area of the electrode pad 9 and the measurement results of the light emission output, forward voltage, and energy efficiency of the light-emitting element 1 when energized with 20 mA.

  FIG. 4A is a graph for explaining the relationship between the area of the electrode pad of the light emitting element and the light emission output according to Example 1 of the present invention. FIG. 4B is a graph for explaining the relationship between the area of the electrode pad and the forward voltage of the light emitting device according to Example 1 of the invention. FIG. 4C is a graph for explaining the relationship between the area of the electrode pad and the energy efficiency of the light emitting device according to Example 1 of the invention.

When the area of the electrode pad 9 is 12000 μm ² or more, the ratio of the area of the electrode pad 9 to the laminated structure 10 increases, causing light absorption, and the light emission output decreases.

  Furthermore, since the light emitting area is reduced at the same time as the area is increased, the current distribution in the chip becomes local, and the forward voltage increases. As a result, energy efficiency is also reduced.

  In Example 2, the light emitting device 1 was manufactured by changing the area of the surface electrode (first electrode 70). At this time, the electrode pad 9 electrode had a diameter of 100 μm, and the distance between the first electrode 70 and the second electrode 50 in the thickness direction of the light-emitting element 1 was 12 μm.

  Further, the structure of the light-emitting element 1 shown in FIG. 1 was manufactured by changing the number of pairs of the first electrode 70 and the second electrode 50 in accordance with each shape parameter.

  5A to 5C show measurement results of the total area of the first electrode 70, the light emission output at the time of energizing 20 mA, and the forward voltage for each area of the first electrode 70.

  FIG. 5A is a graph for explaining the relationship between the total area of the first electrodes and the light emission output of the light emitting device according to Example 2 of the present invention. FIG. 5B is a graph for explaining the relationship between the total area of the first electrodes and the forward voltage of the light emitting device according to Example 2 of the invention. FIG. 5C is a graph for explaining the relationship between the total area of the first electrodes and the energy efficiency of the light emitting device according to Example 2 of the present invention.

  As the area of one first electrode 70 is smaller, the light absorption factor can be reduced and the light emission output becomes higher. However, if the area of the first electrode 70 is too small, the forward voltage increases due to the contact resistance between the first electrode 70 and the laminated structure 10.

In this example, it was found that the forward voltage increased when the area of the first electrode 70 was less than 1 μm ² . In addition, it is considered that the variation in accuracy occurs as the size of the first electrode 70 is reduced.

Moreover, when the area of the 1st electrode 70 becomes large, the influence which absorbs light will become large and the light emission output will fall. Note that even if the area of the first electrode 70 is increased, the forward voltage is not significantly reduced because the contact resistance is sufficiently low. In the present example, it was considered that the area of the first electrode 70 was 100 μm ² or less.

[Other embodiments]
In the configuration described in the embodiment, even when the driving current of the light emitting element 1 is 100 mA, the first electrode 70 and the second electrode 50 are increased in total area (or total number) to increase the first electrode. It was found that even when the area per one of the 70 and the second electrode 50 is small, for example, even when the area is 1 μm ² , an increase in the forward voltage can be suppressed.

  In the case where the light emitting element 1 is 150 μm square and the driving current is 20 mA or less, for example, 5 mA, an output corresponding to the injected power can be obtained in the configuration described in the embodiment.

Moreover, the light emitting element 1 was produced by changing the film thickness of the transparent conductive film 71 in the range of 30 nm to 1 μm. When the area of the light emitting layer 63 of the light emitting element 1 was 150,000 μm ² , the current was dispersed by setting the film thickness to 50 nm, and a predetermined output was obtained. When the film thickness of the transparent conductive film 71 is larger than 1 μm, the light emission output of the light-emitting element 1 is not improved, and the transmittance of the transparent conductive film 71 is decreased.

[Other embodiments]
In addition, in said Embodiment and Examples 1-3, each structure is not limited to the content described, A various deformation | transformation is possible in the range which does not deviate from the meaning of this invention. For example, the following modifications are possible.
(1) In the embodiments and examples, the Si substrate 3 is used as the support substrate. However, other materials can be used as long as the support substrate can withstand the LED element process. Specific examples include a Ge substrate, a GaAs substrate, a GaP substrate, and other metal substrates.
(2) Although the active layer 63 is a bulk layer, it may be a multiple quantum well or the like.
(3) Except for the wavelength dependency of the reflective metal film 4 and the transparent conductive film 71, the present invention can obtain the above-described effects without depending on the wavelength of the emitted light.
(4) In the embodiment and the example, the ohmic contact junction is formed from a single piece, but the above-described effects can be obtained in the same manner even if it is formed from a plurality of pieces.
(5) In the embodiments and examples, the first electrode 70 and the second electrode 50 are circular. This is because in an electrode having a corner, current concentration may occur in the corner. However, if such a point does not cause a problem, a polygonal shape may be used. In the polygonal shape, the lengths of the respective sides may be different, but it is preferable that the lengths of the respective sides are equal from the viewpoint of ease of manufacture and alignment.

DESCRIPTION OF SYMBOLS 1 Light emitting element 1A Light emitting element 2 Back surface electrode 3 Support substrate (Si substrate)
4 reflective metal film 8 transparent insulating film 9 electrode pad 10 laminated structure 40 reflective metal layer 41 metal adhesion layer 50 second electrode 51 transparent insulating film 60 P-type contact layer 61 P-type cladding layer 63 active layer 64 N-type cladding layer 65 N Type contact layer 66 etching stop layer 67 GaAs substrate 70 first electrode 71 transparent conductive film 90 distribution electrode

Claims (12)

A support substrate;
A III-V group compound having a first surface as a light extraction surface, a second surface facing the first surface, and a light emitting layer between the first surface and the second surface A laminated structure composed of semiconductors;
A reflective metal film that is provided between the support substrate and the second surface and reflects the light emitted from the light emitting layer toward the first surface;
A transparent insulating film provided between the interface of the reflective metal film and the semiconductor layer;
A second electrode that penetrates a part of the transparent insulating film and conducts the second surface and the reflective metal film;
A plurality of first electrodes provided on a part of the first surface and electrically conductive with the stacked structure;
A transparent conductive film provided on the first surface and electrically conductive with the first electrode;
An electrode pad provided on the transparent conductive film,
The average value of the distance between the first electrode and the second electrode at the shortest position with respect to the first electrode in plan view is 5 μm or more and 50 μm or less, and 70% of the distance is within ± 20 μm of the average value. And the shortest distance between the pad electrode and the first electrode or the second electrode is 10 μm or more,
In the stacked structure, the light emitting layer has an area of 150,000 μm ² or less.   2. The light emitting device according to claim 1, wherein the first electrode is disposed outside a region where a region where the pad electrode is provided is projected on the first surface in a plan view.   3. The light emitting element according to claim 1, wherein the second electrode is disposed outside a region where the region where the first electrode is provided is projected on the first surface in a plan view.   4. The second electrode according to claim 1, wherein the second electrode is disposed outside a region where the region where the electrode pad is provided is projected on the first surface in plan view. 5. Light emitting element.   The light emitting element according to any one of claims 1 to 4, wherein the second electrode is disposed at a substantially equal distance from the first electrode in a plan view.   The light emitting device according to any one of claims 2 to 5, wherein the laminated structure has a concavo-convex shape formed on a surface of the first surface. The light emitting element according to claim 1, wherein one area of the first electrode is 1 μm ² or more and 100 μm ² or less.   The light-emitting element according to claim 1, wherein the transparent conductive film has a thickness of 50 nm to 1.0 μm.   The light emitting device according to any one of claims 1 to 6, wherein the laminated structure has an N-type conductivity type on the first surface side and a P-type conductivity type on the second surface side. . The light emitting device according to claim 1, wherein an area of the metal pad electrode is 3500 μm ² or more and 12000 μm ² or less. The stacked structure includes a contact layer made of Al _x Ga _1-x As (where 0 ≦ x ≦ 0.3) between the first electrode and the contact layer, and the contact layer is the distribution electrode in a plan view. The light-emitting element according to claim 1, wherein the light-emitting element is formed in a region other than a region in which is formed. The transparent conductive film is made of ITO (tin-doped indium oxide), SnO ₂ (tin oxide), In ₂ O ₃ (indium oxide), or ZnO (zinc oxide) formed by any one of a vacuum deposition method and a sputtering method. , AZO (aluminum-doped zinc oxide), GZO (gallium-doped zinc oxide) or TiO ₂ (titanium oxide), or a structure in which a plurality of these layers are formed, and a resistance of at least 1 × 10 ⁻³ Ω · cm or less The light emitting element of Claims 1-6 which has a rate.

Images