JP2012069684A - Light emitting element - Google Patents

Abstract

A light-emitting element having an electrode structure capable of spreading a current over the entire chip without increasing the light absorption rate is provided.
A light-emitting element includes a first surface serving as a light extraction surface and a second surface facing the first surface, and a stacked layer made of a III-V group compound semiconductor having a light-emitting layer. The structure 10, the reflective metal film 4 provided between the support substrate 3 and the second surface and reflecting the light emitted from the light emitting layer 63 toward the first surface, and a plurality of reflective metal films 4 provided on a part of the first surface. The first electrode 70 electrically conductive with the laminated structure 10, the transparent conductive film 71 provided on the first surface and electrically conductive with the first electrode 70, and the electrode pad 9 provided on the transparent conductive film 71.
[Selection] Figure 1

Description

  The present invention relates to a light emitting element.

  Conventionally, as shown in FIG. 8B, 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. 8A, 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 large light-emitting element (large chip size) having an area of a predetermined size or more, and for example, in a light-emitting element designed for a drive current of DC 100 mA or more, current is stacked 10 However, when the light emitted from the active layer 63 is extracted to the outside of the chip, the distribution electrode 90C absorbs the light so that the light extraction efficiency is reduced. There is a problem of end up.

  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 that reflects on the surface side of the first electrode, a plurality of first electrodes that are provided on a part of the first surface and that conducts with the stacked structure, and a conductor that is provided on the first surface and that conducts with the first electrode There is provided a light emitting device including a transparent conductive film and an electrode pad provided on the transparent conductive film.

  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.

  Further, in the light emitting element, between the reflective metal film interface and the semiconductor layer, the transparent insulating film, and a part of the transparent insulating film are penetrated to conduct the second surface and the reflective metal film. And a second electrode.

  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 film thickness and the transmittance of the transparent conductive film of the light emitting device according to the embodiment of the present invention. FIG. 4 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. 5 is a schematic plan view for explaining the structure of a light emitting device according to a modification of the present invention. FIG. 6A is a graph for explaining the relationship between the area of the electrode pad and the light emission output of the light emitting element according to Example 1 of the present invention. FIG. 6B 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. 7A 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. 7B 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 present invention. FIG. 8A is a schematic plan view for explaining the structure of a conventional light emitting device, and FIG. 8B is a schematic cross-sectional view taken along the line BB in FIG. 8A.

[Summary of embodiment]
A laminated structure including a supporting substrate, a first surface as a light extraction surface, and a second surface opposite to the first surface, and a III-V group compound semiconductor having a light emitting layer; In a light emitting device including a reflective metal film provided between a substrate and the second surface and reflecting the light emitted from the light emitting layer toward the first surface, a plurality of the light emitting elements are provided on a part of the first surface. A light emitting device comprising: a first electrode that is electrically conductive with the laminated structure; a transparent conductive film that is provided on the first surface and that is electrically conductive with the first electrode; and an electrode pad that is provided on the transparent conductive film. Provided.

[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.

Since the transparent conductive film 71 functions as a role of spreading the current in the surface of the light emitting element 1, it has a resistivity of at least 1 × 10 ⁻³ Ω · cm, and the film thickness is preferably at least 50 nm. .

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

  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 addition, the width of the portion where the transparent insulating film 8 is formed in the light emitting element 1 (including the thickness of the transparent insulating film 8) is preferably equal to or less than the width of the support substrate 3.

  When the transparent insulating film 8 is also provided on the light extraction surface side, a separation region may be formed so that the periphery of the electrode pad 9 and the transparent insulating film 8 do not come into contact with each other. This is for suppressing the stress generated in the electrode pad 9 by the transparent insulating film 8.

  FIG. 3 is a graph for explaining the relationship between the film thickness and the transmittance of the transparent conductive film of the light emitting device according to the embodiment of the present invention.

  As a material constituting the transparent conductive film 71, ITO or the like can be used. FIG. 3 shows the relationship between the film thickness of the transparent conductive film 71 and the transmittance for emitted light having a wavelength of 630 nm. When the film thickness of the transparent conductive film 71 is 1.0 μm or more, the light absorption rate of the transparent conductive film 71 is large, and the light emission output of the light emitting element 1 is small. Therefore, it is preferable that the transparent conductive film 71 has a thickness of 1.0 μm or less.

  In addition, for example, in the case of a large chip size LED of 1 mm square in plan view, if the transparent conductive film 71 has a film thickness of 1.0 μm, the current cannot be sufficiently dispersed, so that the diagonal from the electrode pad 9 It is necessary to form the distribution electrode 90 extending in the direction. On the other hand, the distribution electrode 90 preferably has a small area in order to absorb light. However, since the light-emitting element 1 of the present embodiment is based on the premise that a large current is applied, if the cross-sectional area of the distribution electrode 90 is too small, the distribution electrode 90 may be disconnected. Therefore, the cross-sectional area needs to be a predetermined value or more. In addition, it is not preferable to increase the width of the distribution electrode 90 from the viewpoint of light extraction, and as a result of examination, it has been found that the output of light falls when it exceeds 20% of the area of the active layer 63. Therefore, the area is preferably 20% or less of the area of the active layer 63. For example, the width of the distribution electrode 90 is preferably 1.0 μm or more and 20 μm or less, and the height is 500 nm or more.

  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 20000Myuemu ² or less there is 3500 ² or more in plan view. The reason why the upper limit is set to 20000 μm ² is that it has been found that if the size is made larger than this, the light extraction efficiency decreases.

Since the large-sized (large chip size) light-emitting element targeted in this embodiment is used for application of a large current, the resistance between the stacked structure 10 and the first electrode 70 and the second electrode 50 is large. As a series resistance component, the forward voltage increases. Therefore, the plurality of first electrodes 70 are more than the area that does not contribute to the voltage increase estimated from the contact resistance between the metal electrode and the contact layer, and the smaller the smaller the better. Further, it is effective if the light emitted from the active layer 63 is of a size that does not significantly affect the absorption factor. Specifically, the area of each first electrode 70 is preferably 100 μm ² or less. .

If the total area where the contact layer and the first electrode 70 are in contact with each other is small, the forward voltage becomes a factor as a series resistance component. Therefore, the total area where the contact layer and the first electrode 70 are in contact is preferably 100 μm ² or more.

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. 4 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. 4, 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 about 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, an 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, as shown in FIG. 2E, a first electrode 70 is formed on the entire surface of the N-type contact layer 65 by vacuum deposition. The first electrode 70 is formed by sequentially depositing AuGe (gold / germanium alloy), Ti, and Au, respectively.

  Next, using a general photolithography technique such as a resist or a mask aligner, the first electrode 70 is formed as shown in FIG. 2F. Thereafter, the first electrode 70 is left only in a predetermined region, and the N-type contact layer 65 in a region other than the first electrode 70 is removed by etching using an etchant composed of a mixture of sulfuric acid, hydrogen peroxide solution, and water. Then, 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. As an example, the ITO film is formed to a thickness of 500 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.

  A back electrode made of Ti and Au is formed on the back surface of the Si substrate by a vacuum deposition method. The alloy process, which is alloying of the electrodes, is performed by heating to 400 ° C. in a nitrogen gas atmosphere and heat treating for 5 minutes. 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.

  As described above, the LED epitaxial wafer, which was attached to the support substrate through the reflective metal film and the ohmic contact junction and formed with electrodes, was cut using a dicing apparatus, and an LED bare chip having a chip size of 800 μm square was produced. Further, the LED bare chip is mounted on a TO-46 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, and a distribution electrode 90 with a width of 3.0 μm is disposed. 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 between the first electrode 70 and the second electrode 50 in the thickness direction of 1 is 12 μm.

  The light-emitting element 1 was molded with an epoxy resin, and the characteristics as an LED when a current of 500 mA was applied were light output, forward voltage was 380 mW, 2.01 V, and energy efficiency was 37.8%.

(Effect of embodiment)
By performing current dispersion in the plane of the light emitting element 1 by both the transparent conductive film 71 and the first electrode 70 which is a distribution electrode, the area of the first electrode 70 can be reduced as compared with the conventional light emitting element shown in FIG. It became possible to do. That is, the surface electrode area that becomes a light absorption factor is significantly reduced, and the transparent conductive film 71 made of an ITO film is formed with a film thickness that is less affected by light absorption as shown in FIG. The output has been 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.

  FIG. 5 is a schematic plan view for explaining the structure of a light emitting device according to a modification of the present invention.

  The light emitting element 1A was manufactured by removing the distribution electrode 90 from the structure shown in the above embodiment, and the LED characteristics at the time of conducting 500 mA were examined. As a result, the light emission output and the forward voltage were 350 mW and 2.45 V. . The energy efficiency was 28.6%. Without the distribution electrode 90, the current cannot be spread uniformly over the entire light emitting element 1, and the current is concentrated, which is considered to be because the forward voltage is increased. Further, when the current is concentrated, the temperature of the active layer 63 is increased even when the applied current is the same value, so that the internal quantum efficiency is decreased and the light emission output is decreased.

  In addition, when the light emitting elements 1 and 1A of the conventional example (FIG. 8) and this example (FIGS. 1 and 5) were energized at 1.0 A for 1000 hours in a room temperature environment, the characteristics before energization were evaluated at 500 mW. Table 1 shows the relative light output and the change rate of the forward voltage.

As shown in Table 1, it can be seen that the structure with the distribution electrode 90 of the present embodiment is most excellent in the relative light emission output and the forward voltage change rate. This is because the current is uniformly spread to the light emitting element 1 by the distribution electrode 90, and the effective current density of the active layer 63 is reduced. Therefore, the temperature rise of the active layer 63 is suppressed, and the chip deterioration proceeds. Is thought to be slow.

  An 800 μm square light-emitting element having the structure of the light-emitting element described in Embodiment Mode was 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.

  6A and 6B show the area of the electrode pad 9 and the measurement results of the light emission output and forward voltage of the light-emitting element 1 when energized with 500 mA.

  FIG. 6A is a graph for explaining the relationship between the area of the electrode pad and the light emission output of the light emitting element according to Example 1 of the present invention. FIG. 6B is a graph for explaining the relationship between the area of the electrode pad and the forward voltage of the light emitting element according to Example 1 of the invention.

When the area of the electrode pad 9 is 20000 μm ² or more, the ratio of the area of the electrode pad 9 to the laminated structure 10 increases, which becomes a light absorption factor, 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.

  7A and 7B show the measurement results of the total area of the first electrode 70, the light emission output at the time of energization of 500 mA, and the forward voltage for each area of the first electrode 70.

  FIG. 7A 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. 7B 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.

As the area of one first electrode 70 is smaller, the light absorption factor can be reduced and the light emission output becomes higher. When the area of one first electrode 70 is 100 μm ² or more, the light emission output is significantly reduced.

Further, when the total area of the first electrode 70 is small (400 μm ² or less), a forward voltage rise due to contact resistance between the first electrode 70 and the laminated structure 10 occurs. When the total area of the first electrode 70 is 100 μm ² or less, the increase in the forward voltage is particularly significant.

Therefore, the area of one first electrode 70 is preferably as small as possible, and is preferably at least 100 μm ² or less. Furthermore, if the total area of the first electrode 70 is too small, an increase in the forward voltage is caused. Therefore, the total area is preferably at least 100 μm ² or more.

In the above embodiment, the structure of the transparent conductive film 71 has been studied, and in order for the transparent conductive film 71 to function as a role of spreading the current to the large chip size, at least 1 × 10 ⁻³ Ω · cm. It has been found that it has the following resistivity, and that the film thickness of the transparent conductive film 71 is preferably at least 50 nm or more. When the film thickness was less than 50 nm, it was necessary to widen the distribution electrode 90 extending from the electrode pad 9 (increase the area).

  By distributing the current by combining the distribution electrode 90 and the transparent conductive film 71, the area of the distribution electrode 90 can be reduced as compared to the conventional configuration shown in FIG. 20% or less), thereby improving the light extraction efficiency.

[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 embodiment and the example, the shape of the second electrode 50 is formed in a circle surrounding the first electrode in plan view. This is because if the electrode has a corner portion, current concentration may occur at the corner portion. However, if there is no such problem, the electrode is not limited to a circular shape and may have other shapes such as a polygonal shape. There may be. Further, the second electrode 50 may not have a shape surrounding the first electrode 70.
(6) In the embodiments and examples, the first electrode 70 and the second electrode 50 are circular, but may be polygonal as in (5) above. 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 between the layers.

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 (16)

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 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;
A light emitting device comprising: an electrode pad provided on the transparent conductive film.   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.   A transparent insulating film between the reflective metal film interface and the semiconductor layer; and a second electrode that penetrates a part of the transparent insulating film and conducts the second surface and the reflective metal film. The light emitting element of Claim 1 or 2 provided.   4. The light emitting element according to claim 3, 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.   5. The light-emitting element according to claim 3, 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 a plan view.   The light emitting element according to any one of claims 2 to 5, wherein the second electrode is disposed at a substantially equal distance from each of the first electrodes in a plan view.   The light emitting device according to any one of claims 2 to 6, wherein the laminated structure has a concavo-convex shape formed on a surface of the first surface. The light emitting device according to claim 1, wherein the laminated structure has an area of the light emitting layer of 150,000 μm ² or more.   The light emitting device according to claim 8 has a drive current DC of 100 mA or more. The first electrode has one area of 100 μm ² or less, and a total area of contact between all the first electrodes and the laminated structure is 100 μm ² or more. The light emitting element in any one of. The total area of contact between the second electrode and the second surface is 100 μm ² or more;
In plan view, an average value of the distance between the first electrode and the second electrode 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 pad electrode and the first electrode or The light emitting element according to claim 3, wherein the shortest distance to the second electrode is 10 μm or more.   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 8, 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. . And the area of the metal pad electrode 3500 ² or more 20000Myuemu ² or less, or less width 1.0μm or 20μm extending from the edge of the metal pad electrodes, are disposed 0.5 [mu] m ² or more distribution electrode cross-sectional area, further The light-emitting device according to claim 1, wherein the distribution electrode area is 20% or less of the active layer area. 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 14, 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 1-8 which has a rate.

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