JP4894411B2 - Semiconductor light emitting device - Google Patents

Description

  The present invention relates to a semiconductor light emitting device with improved light extraction efficiency.

  In recent years, light-emitting diodes (LEDs), which are semiconductor light-emitting elements, have been capable of growing GaN-based and AlGaInP-based high-quality crystals by the MOVPE method, so that blue, green, orange, yellow, red, etc. High brightness LED can be manufactured. Along with the increase in brightness of LEDs, the use is expanding to brake lamps for automobiles, backlights for liquid crystal displays, and the like, and demand is increasing year by year.

  Since high quality crystals can be grown by the MOVPE method, the luminous efficiency inside the light emitting element is approaching the limit value of the theoretical value. However, the light extraction efficiency from the light emitting element to the outside is still low, and improvement of the light extraction efficiency is desired.

  For example, a high-brightness red LED is formed of an AlGaInP-based material and sandwiched between an n-type AlGaInP layer and a p-type AlGaInP layer made of an AlGaInP-based material having a lattice-matched composition on a conductive GaAs substrate. It has a double hetero structure having a light emitting layer (active layer) made of AlGaInP or GaInP. At this time, since the band gap of the GaAs substrate is narrower than the band gap of the light emitting layer, most of the light from the light emitting layer is absorbed by the GaAs substrate, and the light extraction efficiency decreases.

  As a countermeasure, light absorption at the GaAs substrate is reduced by reflecting the light toward the GaAs substrate by forming a multilayer reflective film structure layer made of semiconductors having different refractive indexes between the light emitting layer and the GaAs substrate. There is a method for improving the light extraction efficiency. However, this method reflects only light having a limited incident angle with respect to the multilayer reflective film structure layer.

  Therefore, there is a patent for a method in which a double heterostructure layer made of an AlGaInP-based material is attached to a support substrate such as Si or GaAs via a highly reflective metal layer, and then the GaAs substrate used for growth is removed. It is disclosed in Document 1. If this method is used, since a metal is used as the reflection layer, reflection with a high reflectance can be performed without selecting an incident angle with respect to the reflection layer.

  FIG. 11 shows the structure of a conventional semiconductor light emitting device. As shown in the figure, a conventional semiconductor light emitting device 111 includes a semiconductor 3 formed by laminating a plurality of layers including a light emitting layer 2, a reflective metal layer 4 covering one main surface S2 side of the semiconductor 3, and this reflection. The ohmic contact junction 5 formed at the interface between the metal layer 4 and the semiconductor 3 and arranged discretely on the surface of the reflective metal layer 4 and the one main surface S2 side of the semiconductor 3 outside the reflective metal layer 4 are covered. A back electrode 8, a front electrode 9 that partially covers the other main surface (light extraction surface) S1 of the semiconductor 3, and a support substrate 15 that supports the entire surface from the back electrode 8 to the front electrode 9 are provided.

JP 2002-217450 A

  The reflective metal layer 4 provided between the double heterostructure layer (semiconductor 3) made of an AlGaInP-based material and the support substrate 15 naturally has a high reflectivity, and the semiconductor 3 made of an AlGaInP-based material Ohmic contact must be made. However, it is difficult to make an ohmic contact directly with an AlGaInP-based material using a metal such as Ag, Al, or Au having a high reflectance with respect to the light emission wavelength of light from the AlGaInP-based light emitting layer 2. Therefore, it is necessary to partially arrange the ohmic contact junction 5 between the reflective metal layer 4 and the semiconductor 3. The partial arrangement means not to cover the entire surface of the reflective metal layer 4 but to disperse it on the surface.

  The ohmic contact junction 5 is disposed between the reflective metal layer 4 and the semiconductor 3 in order to obtain an ohmic contact, and has a lower reflectance than the reflective metal layer 4. Further, in order to obtain ohmic contact, it is necessary to perform heat treatment after the ohmic contact junction 5 is formed on the semiconductor 3 (in the reflective metal layer 4). During the heat treatment, an alloying reaction occurs between the semiconductor 3 and the ohmic contact junction 5, and the light absorption rate increases in the portion of the semiconductor 3 that is in contact with the ohmic contact junction 5. For this reason, light generated at a location overlapping the ohmic contact junction 5 in the light emitting layer 2 has a larger light absorption than light generated at other locations.

  As described above, as a result of the low reflectance of the ohmic contact junction 5 and the large light absorption, the conventional semiconductor light emitting device 111 has a reduced light extraction efficiency of the entire light emitting device.

  By reducing the area of the ohmic contact junction 5 as much as possible, light absorption by the ohmic contact junction 5 can be reduced and light extraction efficiency can be increased. However, in order to drive a semiconductor light emitting device at a low voltage, a certain level or more is required. The area ohmic contact junction 5 is required. Therefore, there is a limit to reducing the area of the ohmic contact junction 5.

  Further, in the conventional semiconductor light emitting device 111, the surface electrode 9 overlaps the light extraction surface S1. For this reason, the light produced in the part which overlaps with the surface electrode 9 in the light emitting layer 2 is interrupted by the surface electrode 9, and cannot be taken out. For this reason, the light extraction efficiency of the entire light emitting element is lowered.

  Accordingly, an object of the present invention is to provide a semiconductor light emitting device that solves the above problems and improves the light extraction efficiency.

  To achieve the above object, the present invention provides a semiconductor formed by laminating a plurality of layers including a light emitting layer, a reflective metal layer covering one main surface side of the semiconductor, the reflective metal layer, and the semiconductor. And an ohmic contact junction formed discretely on the surface of the reflective metal layer, and a void formed at a location overlapping the ohmic contact junction in the light emitting layer.

  It may have a reaction suppression layer sandwiched between the reflective metal layer and the semiconductor, and the ohmic contact junction may be formed from the reflective metal layer to the semiconductor through the reaction suppression layer.

  The void may be formed by making a hole in the semiconductor from the other main surface side.

  The semiconductor may have a conductive layer in contact with the ohmic contact junction and another semiconductor layer in contact with the conductive layer from the opposite side of the ohmic contact junction.

  The semiconductor includes a first conductive layer and a second conductive layer sandwiching the light emitting layer, and the first conductive layer and the second conductive layer on the main surface side opposite to the reflective metal layer. The positioned conductive layer may have a lower resistance.

  An electrode that partially covers the main surface may be disposed on the other main surface of the semiconductor, and the ohmic contact junction may be disposed at a location that does not overlap the electrode.

  The present invention exhibits the following excellent effects.

  (1) The light extraction efficiency is improved.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIGS. 1A and 1B, a semiconductor light emitting device 1 according to the present invention includes a semiconductor 3 formed by laminating a plurality of layers including a light emitting layer 2, and one of the semiconductors 3. A reflective metal layer 4 covering the main surface side S2 of the substrate, an ohmic contact junction 5 formed discretely on the surface of the reflective metal layer 4 formed at the interface between the reflective metal layer 4 and the semiconductor 3, and the light emitting layer 2 And an air gap 6 formed at a location overlapping the ohmic contact junction 5 inside.

  Further, the semiconductor light emitting device 1 includes a back electrode 8 that covers one main surface S2 of the semiconductor 3 outside the reflective metal layer 4 and a surface electrode 9 that partially covers the other main surface of the semiconductor 3.

  The semiconductor 3 is a III-V group compound semiconductor. For example, the Mg-GaP contact layer 10, the Mg-AlGaInP cladding layer 11, the AlGaInP active layer (light emitting layer) 2, the Si-AlGaInP cladding layer 12, and the Si-GaAs contact layer. 13 is provided. After the Si-GaAs contact layer 13 is formed over the entire surface, it is partially removed by etching, and is left only at the portion overlapping the surface electrode 9. The main surface of the Si—AlGaInP cladding layer 12 is defined as a first main surface S1 of this semiconductor. The first main surface S1 is a light extraction surface. The main surface of the Mg—GaP contact layer 10 is defined as a second main surface S2 of this semiconductor. The second main surface S2 is a reflective surface covered with the reflective metal layer 4.

  Furthermore, the semiconductor light emitting device 1 includes a metal adhesion layer 14 and a Si—GaAs support substrate 15 between the reflective metal layer 4 and the back electrode 8.

  As shown in FIG. 1A, when viewed from the light extraction surface S1, the semiconductor 3 is formed in a substantially square shape, and the surface electrode 9 is concentrated in a circle mainly at the central portion of the light extraction surface, and is radially formed from the central portion. And having a plurality of branches extending in the direction.

  The ohmic contact junctions 5 are arranged at a plurality of locations at regular intervals in the vertical and horizontal directions on the surface of the reflective metal layer 4, and each is formed in a small circle. In the light emitting layer 2, small circular gaps 6 are formed so as to exactly overlap the respective ohmic contact junctions 5. In this embodiment, a hole 16 is opened from the first main surface S1 side, which is a light extraction surface, to the second main surface S2 until just before the Mg—GaP contact layer 10, and the Si—AlGaInP clad layer 12 emits light. Since the hole 16 penetrates the layer 2 and the Mg—AlGaInP clad layer 11, the air gap 6 is formed in the light emitting layer 2. Thereby, it becomes the shape where a part of 1st main surface S1 is dented in concave shape. The hole 16 is formed by etching, for example.

  According to the semiconductor light emitting device 1 shown in FIG. 1A and FIG. 1B, the gap 6 is formed at a location overlapping the ohmic contact junction 5 in the light emitting layer 2. The current injected into the semiconductor 3 through the ohmic contact junction 5 is concentrated on the enriched portion of the light emitting layer 2 avoiding the gap 6. In the light emitting layer 2, current flows only in the enriched portion and contributes to light emission, so that the light traveling toward the second main surface S 2 reaches the reflective metal layer 4 without passing through the ohmic contact junction 5. Similarly, the reflected light from the reflective metal layer 4 returns to the semiconductor 3 without passing through the ohmic contact junction 5, and travels toward the first main surface S1.

  As described above, since the current flows only in the portion (solid portion) that does not overlap the ohmic contact junction 5 in the light emitting layer 2, the light emitted by the current does not pass through the ohmic contact junction 5. For this reason, light absorption in the ohmic contact junction 5 is avoided, and light generated from the current injected into the semiconductor 3 is efficiently emitted from the first main surface S1, and the light extraction efficiency of the entire light emitting element is increased. Will improve. As a result, a light-emitting element with high efficiency and high brightness is realized.

  Next, another embodiment will be described.

The semiconductor light emitting device 21 shown in FIGS. 2A and 2B is basically the same as the semiconductor light emitting device 1 shown in FIGS. 1A and 1B. The reaction suppression layer 22 is sandwiched between the reflective metal layer 4 and the semiconductor 3. An ohmic contact junction 23 is formed from the reflective metal layer 4 to the Mg—GaP contact layer 10 of the semiconductor 3 through the reaction suppression layer 22. The reaction suppression layer 22 is made of a low-reaction and transparent material such as SiO ₂ or SiN, and is transparent at the emission wavelength. In addition, the reflective metal layer 4 and the semiconductor 3 are used in the heat treatment process in the process of manufacturing the semiconductor light-emitting element 22. It has the function to suppress the reaction with. Thereby, the reflectance of the reflective metal layer 4 is kept high even after the heat treatment step, and the light extraction efficiency is improved.

  The semiconductor light emitting device 31 shown in FIGS. 3A and 3B is basically the same as the semiconductor light emitting device 21 shown in FIGS. 2A and 2B. The ohmic contact junction 5 is not disposed at a location overlapping the surface electrode 9 provided on the first main surface S1. In other words, the ohmic contact junction 5 is disposed only at a location that does not overlap the surface electrode 9. Along with this, the gap 6 of the light emitting layer 2 is not disposed at a location overlapping the surface electrode 9. That is, in the semiconductor light emitting element 31, the ohmic contact junction 5 and the gap 6 indicated by the thin lines in FIG. 2B are not formed.

  In this semiconductor light emitting device 31, since the ohmic contact junction 5 is not formed at a location overlapping the surface electrode 9, the current flowing in the location overlapping the surface electrode 9 is reduced in the light emitting layer 2, and light emission is suppressed at that location. The On the contrary, the current flowing through the portion that does not overlap the surface electrode 9 increases, and the light generated there is taken out without being obstructed by the surface electrode 9. As a result, the light extraction efficiency of the entire light emitting element is improved.

  Note that the effect of reducing the current flowing in the light emitting layer 2 where it overlaps the surface electrode 9 is that the n-type cladding layer (Si-AlGaInP cladding) located closer to the light extraction surface (first main surface S1) than the light emitting layer 2 is. This is due to the large current spreading effect in layer 12). This is a phenomenon that occurs because the resistance of the n-type cladding layer is lower than that of the p-type cladding layer (Mg—AlGaInP cladding layer 11). Thus, of the first conductive layer and the second conductive layer sandwiching the light emitting layer 2, the Si—AlGaInP cladding layer 12, which is a conductive layer located on the main surface S 1 side opposite to the reflective metal layer 4, is formed. Since the resistance is lower, a current dispersion effect in the Si—AlGaInP cladding layer 12 is obtained, which contributes to an improvement in light extraction efficiency.

  In the embodiments so far, the AlGaInP active layer (light emitting layer) 2 is an undoped bulk layer, but the effect of the present invention can be obtained even when the active layer is a multiple quantum well or a strained quantum well.

  The semiconductor light emitting elements 1, 11, 21 are, for example, red LEDs having an emission wavelength of 630 nm. Even in an LED having an emission wavelength of 560 nm to 660 nm made of the same AlGaInP-based material, the material, carrier concentration, and contact layer of each layer may be appropriately determined as is well-known and commonly used. Even in such a case, the effects of the present invention can be obtained. It is done.

  The shape of the surface electrode 9 is not limited to a circle or a shape obtained by adding a radial branch to the circle, but may be a quadrangle, a rhombus, a polygon, other different shapes, or a shape obtained by adding a branch of an arbitrary shape. The effects of the invention can be obtained.

  The support substrate is not limited to the Si—GaAs support substrate 15. The effect of the present invention can be obtained even with a semiconductor light emitting device using a Ge support substrate, a Si support substrate, or a metal support substrate.

  In the semiconductor light emitting device 1 of FIG. 1, the electrical continuity between the semiconductor 3 and the reflective metal layer 4 is made by the ohmic contact junction 5. Therefore, if the gap 6 reaches the ohmic contact junction 5, the electrical continuity between the semiconductor 3 and the reflective metal layer 4 is deteriorated. Therefore, even if the gap 6 is formed, it is necessary to leave a conductive layer in contact with the ohmic contact junction 5 immediately above the ohmic contact junction 5. This conductive layer is the Mg—GaP contact layer 10.

  On the other hand, since the selective etching is used to form the void 6, the Mg-GaP contact layer 10 is opposite to the ohmic contact junction 5 as a semiconductor layer having a composition different from that of the conductive layer so that the selective etching is possible. Another semiconductor layer in contact with the side is required. In the semiconductor light emitting device 1 of FIG. 1, the Mg—AlGaInP clad layer 11 serves as another semiconductor layer. Thereby, the formation of the void 6 can be stopped up to the Mg—AlGaInP cladding layer 11, and the void 6 does not reach the Mg—GaP contact layer 10.

  As described above, since there are two or more semiconductor layers having different compositions on the ohmic contact junction 5 side of the light emitting layer 2 of the semiconductor 3, the Mg—GaP contact layer 10 which is a conductive layer in contact with the ohmic contact junction 5. It becomes easy to form the gap 6 by etching leaving

Example 1
A red LED epitaxial wafer having a structure shown in FIG. 4 and having an emission wavelength of about 630 nm was fabricated, and based on this, the semiconductor light emitting device 1 according to the present invention of FIG. 1 was fabricated as an LED device. The epitaxial growth method, the epitaxial layer structure, the thickness of each layer, the formation method of the reflective metal layer and the ohmic contact junction, the replacement method to the support substrate, the electrode formation method, the void formation method, and the LED element production method are as follows: Street.

As shown in FIG. 4, on an n-type GaAs substrate (Si-GaAs substrate) 41, the MOVPE method, n-type _{(Si-doped) (Al 0.7 Ga 0.3) 0.5} In 0.5 P etching stop layer (Si-AlGaInP etching Stop layer: thickness 200 nm, carrier concentration 1 × 10 ¹⁸ / cm ³ ) 42, n-type (Si-doped) GaAs contact layer (Si-GaAs contact layer; thickness 100 nm, carrier concentration 1 × 10 ¹⁸ / cm ³ ) 43 N-type (Si doped) (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer (Si—AlGaInP clad layer; thickness 2000 nm, carrier concentration 1 × 10 ¹⁸ / cm ³ ) 44, undoped (Al _0.1 Ga _0.9 ) _0.5 In _0.5 P active layer (AlGaInP active layer; thickness 900 nm) 45, p-type _{(Mg-doped) (Al 0.7 Ga 0.3) 0.5} In 0.5 Cladding layer (Mg-AlGaInP cladding layer; thickness of 400 nm, carrier concentration ^{1.2 × 10 18 / cm 3)} 46, p -type (Mg-doped) GaP contact layer (Mg-GaP contact layer; thickness of 300 nm, a carrier concentration of 1 × 10 ¹⁸ / cm ³ ) 47 were grown sequentially to obtain a red LED epitaxial wafer 40.

The growth temperature in the MOVPE method was 650 ° C., the growth pressure was 6666 Pa, the growth rate of each layer was 0.3 to 1.0 nm / sec, and the V / III ratio was about 200. The V / III ratio is the ratio when the denominator is the number of moles of a group III material such as trimethylgallium (TMGa) or trimethylaluminum (TMAl) and the molecule is the number of moles of a group V material such as AsH ₃ or PH _3. (Quotient).

As raw materials used in the MOVPE method, organic metals such as trimethylgallium (TMGa), triethylgallium (TEGa), trimethylaluminum (TMA), trimethylindium (TMIn), arsine (AsH ₃ ), phosphine (PH ₃ ), etc. It includes hydride gas, in this example, TMGa, TMA, TMIn, a PH _3, AsH ₃ were used. The III-V group compound semiconductor can be formed by including the group III elements Al, Ga, In and the group V elements P, As in these raw materials.

Disilane (Si ₂ H ₆ ) was used as an additive for determining the conductivity type of the n-type semiconductor layer. In addition, hydrogen selenide (H ₂ Se), monosilane (SiH ₄ ), and diethyl tellurium (DETe) may be used as a conductivity type determining additive for the n-type semiconductor layer.

Biscyclopentadienyl magnesium (Cp ₂ Mg) was used as the conductivity type determining additive of the p-type semiconductor layer. In addition, dimethyl zinc (DMZn) and diethyl zinc (DEZn) may be used as the conductivity type determining additive of the p-type semiconductor layer.

  After carrying out the red LED epitaxial wafer 40 of FIG. 4 from the MOVPE apparatus, as shown in FIG. 5, a general photolithography technique and a vacuum evaporation method using a resist and a mask aligner are formed on the surface of the Mg—GaP contact layer 47. The ohmic contact junction 51 was formed using The ohmic contact junction 51 was made of a gold / zinc (AuZn) alloy. The size and shape of the ohmic contact junction 51 was a circle having a diameter of 15 μm when viewed from the main surface, and the thickness was 50 nm. The arrangement of the ohmic contact junctions 51 was 30 μm pitch vertically and horizontally. Then, the alloy process which is alloying of the ohmic contact junction part 5 was performed. In the alloy process, it was heated to 400 ° C. in a nitrogen gas atmosphere and heat-treated for 5 minutes.

  Next, as shown in FIG. 6, a reflective metal layer 61 covering the ohmic contact junction 51 was formed. The reflective metal layer 61 was formed by evaporating aluminum (Al), titanium (Ti), and gold (Au) in this order to a thickness of 200 nm, 200 nm, and 500 nm, respectively.

  Next, as shown in FIG. 7, a Si—GaAs substrate 72 is prepared for the support substrate 71, and a gold / germanium (AuGe) alloy, titanium (Ti), gold (Au) is added to the Si—GaAs substrate 72. Were deposited in this order to a thickness of 200 nm, 200 nm, and 500 nm, respectively, to form a metal adhesion layer 73 and obtain a support substrate 71.

Next, the red LED epitaxial wafer 40 of FIG. 6 and the support substrate 71 of FIG. 7 were bonded together. Specifically, as shown in FIG. 8, the surface of the reflective metal layer 61 of the red LED epitaxial wafer 40 and the Au surface of the metal adhesion layer 73 of the support substrate 71 were bonded to obtain a bonded product 81. . The pasting was performed by holding at a temperature of 350 ° C. for 60 minutes under a pressure of 1.3 Pa and a load of 30 kgf / cm ² .

  Next, after the surface of the Si-GaAs substrate 72 of the support substrate 71 is protected with a resist for the bonded product 81, the Si-GaAs substrate 41 of the red LED epitaxial wafer 40 is replaced with ammonia water and hydrogen peroxide solution. The Si—AlGaInP etching stop layer 42 was exposed by etching with the mixed solution. Next, the Si—AlGaInP etching stop layer 42 was removed with hydrochloric acid to expose the Si—GaAs contact layer 43. Thereafter, the resist of the Si-GaAs substrate 72 was removed using acetone and methanol.

  Next, as shown in FIG. 9, using a general photolithography technique and a vacuum deposition method using a resist and a mask aligner for the Si-GaAs contact layer 43, a circular central portion having a diameter of 100 μm, A surface electrode 91 having branches having a width of 10 μm extending radially from the center was formed. The surface electrode 91 was formed by evaporating gold / germanium (AuGe) alloy, titanium (Ti), and gold (Au) in this order to a thickness of 100 nm, 100 nm, and 500 nm, respectively.

  After the surface electrode 91 was formed, the Si-GaAs contact layer 43 was etched using an etchant composed of a mixture of sulfuric acid, hydrogen peroxide solution, and water, using the surface electrode 91 as a mask. By this etching, the Si-GaAs contact layer 43 on which the surface electrode 91 overlaps is selectively left, the Si-GaAs contact layer 43 on which the surface electrode 91 does not overlap is removed, and the Si-AlGaInP cladding layer 44 is exposed. .

  Next, as shown in FIG. 10, a resist having a pattern having an opening with a diameter of 15 μm was applied to the surface of the Si—AlGaInP cladding layer 44 by a photolithography technique at a location overlapping the ohmic contact junction 51. Only the opening of the resist was selectively etched using a hydrochloric acid-based etchant, and this etching was performed until the Mg—GaP contact layer 47 was exposed. That is, the Si—AlGaInP cladding layer 44, the AlGaInP active layer 45, and the Mg—AlGaInP cladding layer 46 are continuously etched only by the hydrochloric acid etching. Thereafter, the resist was removed using acetone and methanol.

  Next, as shown in FIG. 10, the back electrode 102 was formed on the entire surface of the Si—GaAs substrate 72 by vacuum deposition. The back electrode 92 is an alloy process in which gold / germanium (AuGe) alloy, titanium (Ti), and gold (Au) are deposited in this order in thicknesses of 60 nm, 10 nm, and 500 nm, respectively, and then the back electrode 92 is alloyed. Went. In the alloy process, it was heated to 400 ° C. in a nitrogen gas atmosphere and heat-treated for 5 minutes.

  Thus, the semiconductor light emitting device 100 shown in FIG. 10 was obtained. This is nothing but a wafer in which a large number of semiconductor light emitting devices 1 in FIG. 1 are assembled.

  In order to separate this semiconductor light emitting element 1 element by element, it was cut into a chip size of 300 μm square using a dicing apparatus so that the center part of the surface electrode 9 was at the center, thereby obtaining an LED bare chip. The LED bare chip was mounted (die bonding) on a TO-18 stem (not shown). Thereafter, wire bonding was performed on the LED bare chip to obtain an LED element (not shown).

  As a result of evaluating the initial characteristics of the LED element, the initial characteristics were a light emission output of 3.60 mW and an operating voltage of 1.94 V when 20 mA was applied (evaluation).

Thus, the LED element of Example 1 has a gap 6 where it overlaps the ohmic contact junction 5 of the light emitting layer 2, so that the current injected into the LED element flows to the substantial part of the light emitting layer 2, Since the emitted light does not pass through the ohmic contact junction 5, the light extraction efficiency is improved.
(Example 2)
A red LED epitaxial wafer 40 having an emission wavelength of about 630 nm and having the structure shown in FIG. 4 was produced, and based on this, the semiconductor light emitting device 21 according to the present invention of FIG. 2 was produced as an LED device. The epitaxial growth method, the epitaxial layer structure, the thickness of each layer, the method of forming the reflective metal layer, the method of replacing the support substrate, the method of forming the electrode, the method of forming the air gap, and the method of manufacturing the LED element are the same as in Example 1. Since the reaction suppression layer is formed and the ohmic contact junction is embedded therein, the method will be described in detail.

A SiO ₂ film having a thickness of 100 nm was formed as a reaction suppression layer (not shown) on the surface of the Mg—GaP contact layer 47 of the red LED epitaxial wafer 40 of FIG. 4 by a plasma CVD method. On the surface of the reaction suppression layer, a resist having a circular opening with an opening diameter of 15 μm is formed at a pitch of 30 μm by a general photolithography technique using a resist and a mask aligner, and SiO ₂ in the opening is formed using a fluorine-based etchant. As a result, a hole was opened and the Mg—GaP contact layer 47 was exposed.

  In the hole of the reaction suppression layer where the Mg—GaP contact layer 47 was exposed, an ohmic contact junction was formed to a thickness of 100 nm, that is, the same thickness as the reaction suppression layer, by vacuum deposition. A gold / zinc (AuZn) alloy was used for the ohmic contact junction.

  Thereafter, the reflective metal layer 61 (FIG. 6) is formed in the same manner as in Example 1. Therefore, in Example 2, the reaction suppression layer sandwiched between the reflective metal layer 61 and the semiconductor (red LED epitaxial wafer 40) is formed. The ohmic contact junction is formed from the reflective metal layer to the semiconductor through the reaction suppression layer. After that, the steps after FIG. 6 were performed in the same manner as in Example 1 to obtain the semiconductor light emitting device 21 of FIG. 2, and then the LED device (not shown) was obtained.

  As a result of evaluating the initial characteristics of the LED element, the initial characteristics were a light emission output of 3.85 mW and an operating voltage of 1.97 V when 20 mA was applied (evaluation).

In the second embodiment, the reaction suppressing layer 22 is provided between the semiconductor 3 and the reflective metal layer 4, so that the process of attaching the reflective metal layer 4 and the Si-GaAs support substrate 15 or the heat treatment process in the electrode alloy process. The effect of suppressing the reaction between the reflective metal layer 4 and the Si-GaAs support substrate 15 is obtained. Thereby, the reflectance of the reflective metal layer 4 is kept high even after the heat treatment step, and the light extraction efficiency is improved.
(Example 3)
A red LED epitaxial wafer 40 having an emission wavelength of about 630 nm and having the structure shown in FIG. 4 was produced, and based on this, the semiconductor light emitting device 31 according to the present invention of FIG. 3 was produced as an LED device. Epitaxial growth method, epitaxial layer structure, thickness of each layer, reflective metal layer, reaction suppression layer, ohmic contact junction formation method, support substrate replacement method, electrode formation method, void formation method, LED element preparation method Is the same as in Example 2, except that the ohmic contact junction 5 is not formed at a location overlapping the surface electrode 9.

  Thus, after obtaining the semiconductor light emitting element 31 of FIG. 3, the LED element which is not illustrated was obtained.

  As a result of evaluating the initial characteristics of the LED element, the initial characteristics were a light emission output of 4.10 mW and an operating voltage of 1.97 V when 20 mA was applied (evaluation).

In Example 3, since the ohmic contact junction 5 is disposed only in a portion that does not overlap with the surface electrode 9, a large amount of current flows in a portion that does not overlap with the surface electrode 9 in the light emitting layer 2, and light generated there is Since the light is extracted without being obstructed by the surface electrode 9, the light extraction efficiency is improved.
(Conventional example)
A red LED epitaxial wafer having a structure as shown in FIG. 4 and an emission wavelength of around 630 nm was fabricated, and based on this, the conventional semiconductor light emitting device 111 of FIG. 11 was fabricated as an LED device. In the meantime, the epitaxial growth method, the epitaxial layer structure, the thickness of each layer, the formation method of the reflective metal layer and the ohmic contact junction, the replacement method to the support substrate, the electrode formation method, and the LED element production method are the same as in Example 1. The only difference is that no voids are formed.

  As a result of evaluating the initial characteristics of the LED element, the initial characteristics were a light emission output of 2.35 mW and an operating voltage of 1.92 V when 20 mA was applied (evaluation). As for this initial characteristic, light emission output is small compared with any of Examples 1-3.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure of the semiconductor light-emitting device which shows one Embodiment of this invention, (a) is the top view seen from the light extraction surface, (b) is sectional drawing along the dashed-dotted line of the top view. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure of the semiconductor light-emitting device which shows one Embodiment of this invention, (a) is the top view seen from the light extraction surface, (b) is sectional drawing along the dashed-dotted line of the top view. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure of the semiconductor light-emitting device which shows one Embodiment of this invention, (a) is the top view seen from the light extraction surface, (b) is sectional drawing along the dashed-dotted line of the top view. It is sectional drawing of the epitaxial wafer for red LEDs produced in the Example. It is sectional drawing of the epitaxial wafer for red LEDs in which the ohmic contact junction part was formed in the Example. It is sectional drawing of the epitaxial wafer for red LEDs in which the reflective metal layer was formed in the Example. It is sectional drawing of the support substrate produced in the Example. It is sectional drawing of the bonded product produced in the Example. It is sectional drawing of the bonded product which formed the surface electrode and etched in the Example. It is sectional drawing of the semiconductor light-emitting device obtained by forming a back surface electrode in a bonded article in the Example. It is sectional drawing of the conventional semiconductor light-emitting device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,11,21 Semiconductor light emitting element 2 Light emitting layer 3 Semiconductor 4 Reflective metal layer 5 Ohmic contact junction part 6 Space | gap 8 Back electrode 9 Surface electrode

Claims (6)

  A semiconductor formed by laminating a plurality of layers including a light emitting layer, a reflective metal layer covering one main surface side of the semiconductor, and a surface of the reflective metal layer formed at the interface between the reflective metal layer and the semiconductor A semiconductor light emitting device comprising: ohmic contact junctions arranged in a discrete manner; and voids formed in portions of the light emitting layer overlapping the ohmic contact junctions.   It has a reaction suppression layer sandwiched between the reflective metal layer and the semiconductor, and the ohmic contact junction is formed from the reflective metal layer to the semiconductor through the reaction suppression layer. The semiconductor light emitting device according to claim 1.   3. The semiconductor light emitting element according to claim 1, wherein the void is formed by making a hole in the semiconductor from the other main surface side.   4. The semiconductor light emitting device according to claim 1, wherein the semiconductor has a conductive layer in contact with the ohmic contact junction, and another semiconductor layer in contact with the conductive layer from the opposite side of the ohmic contact junction. element.   The semiconductor includes a first conductive layer and a second conductive layer sandwiching the light emitting layer, and the first conductive layer and the second conductive layer on the main surface side opposite to the reflective metal layer. The semiconductor light emitting element according to claim 1, wherein the conductive layer located has a lower resistance. 6. The electrode according to claim 1, wherein an electrode that partially covers the main surface is disposed on the other main surface of the semiconductor, and the ohmic contact junction is disposed at a location that does not overlap the electrode. Semiconductor light emitting device.

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