JP2010141225A - Semiconductor light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the efficiency of light extraction from a semiconductor light emitting device. <P>SOLUTION: The semiconductor light emitting device 20 includes a surface electrode 13 formed on the first main surface of a group III-V semiconductor layer 21 having a light emitting layer 5, a reflection metal film 10 formed on a second main surface, a semiconductor layer 21 and a supporting substrate 11 connected through the reflection metal film 10, an ohmic contact joint 9 disposed in a region except just under the surface electrode 13 but in the portion of the face of the semiconductor layer 21 side of the reflection metal film 10. The semiconductor light emitting device 20 is ≤320 μm on a side. The surface electrode 13 has a polygonal or round shape with a circumferential length ≥235 μm and ≤700 μm. The ohmic contact joint 9 is disposed at the outer circumferential side or close to the outer circumference of the semiconductor light emitting device 20. The ohmic contact joint 9 surrounds the surface electrode 13 when viewed from the surface electrode 13 side. The distance L from each circumference position of the surface electrode 13 to the nearest ohmic contact joint 9 is the same. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a semiconductor light emitting device having a structure in which an ohmic contact junction and a metal reflective film are sandwiched between a III-V group compound semiconductor layer having a light emitting layer and a support substrate, and in particular, improvement of light extraction efficiency is achieved. The present invention relates to a semiconductor light emitting device.

  2. Description of the Related Art Conventionally, light emitting diodes (LEDs), which are semiconductor light emitting elements, are blue because GaN-based and AlGaInP-based high-quality crystals can be grown by MOVPE (metal organic vapor phase epitaxy) in recent years. Green, orange, yellow, and red high-brightness LEDs can be manufactured. And with the increase in brightness of LEDs, their uses have spread to automobile brake lamps, liquid crystal display backlights, and the like, and their demand is increasing year by year.

  Currently, since high-quality crystals can be grown by the MOVPE method, the internal efficiency of the light-emitting element is approaching the theoretical limit value. However, the light extraction efficiency from the light emitting element is still low, and it is important to improve the light extraction efficiency. For example, a high-intensity red LED is formed of an AlGaInP-based material, and its light emitting portion includes 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. A double hetero structure having a light emitting layer (active layer) made of AlGaInP or GaInP sandwiched between two layers. However, 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 is significantly reduced.

Therefore, in order to reduce light absorption by the GaAs substrate, the following method has been conventionally employed.
There is a known method for reducing light absorption in a GaAs substrate and improving light extraction efficiency by forming a multilayer reflective film structure composed of semiconductor layers having different refractive indexes between a light emitting layer and a GaAs substrate. Yes. However, with this method, only light having a limited incident angle to the multilayer reflective film structure can be reflected.

  In addition, a double heterostructure made of an AlGaInP-based material is attached to a Si support substrate having a thermal conductivity higher than that of the GaAs substrate through a highly reflective metal reflective film, and then the GaAs substrate used for semiconductor growth is attached. A removal method has been devised (see, for example, Patent Document 1). In the metal reflection film used in this method, high reflection is possible regardless of the angle of incidence of light on the metal reflection film, so that high brightness of the LED is realized.

  In the LED structure in which the metal reflective film is sandwiched between the light emitting layer and the Si support substrate, when a metal having high reflectivity is used as the metal reflective film, specifically, Al, Au, or Ag is used, the compound semiconductor and the electric material are electrically connected. Since ohmic connection cannot be obtained, a part of the metal reflective film is used as an ohmic contact junction. Therefore, the electrons or holes injected into the LED element flow from the surface electrode formed on the light emitting portion through the ohmic contact junction to the Si support substrate. At that time, light is emitted from the active layer between the surface electrode and the ohmic contact junction. The emitted light is extracted from the semiconductor layer surface (light extraction surface) above the light emitting unit to the outside of the light emitting element.

JP 2005-175462 A

  By the way, in the above conventional LED structure in which the ohmic contact junction and the metal reflection film are sandwiched between the light emitting layer and the Si support substrate, a part of the emitted light is between the light extraction surface and the metal reflection film. However, when light reaches the ohmic contact junction and the surface electrode, both the ohmic contact junction and the surface electrode have high absorption for the emitted light, and thus light cannot be extracted outside the light emitting element. . In particular, since the surface electrode has a larger area than the ohmic contact portion, it becomes a large absorption factor in the entire light emitting element. For this reason, it is necessary to reduce the area of the surface electrode. However, in the case of a surface electrode having a simple circular shape or the like, the current dispersibility deteriorates when the area is reduced.

  Therefore, various surface electrode shapes such as a surface electrode having a shape in which the surface electrode is linearly extended from the center of the circular shape (for example, see FIG. 10) are devised so as to uniformly distribute the current in the light emitting element. Thus, not only the light extraction efficiency is improved, but also characteristics such as reduction of the forward voltage are improved.

  However, in order to reduce light absorption at the surface electrode, in the current confinement structure light emitting element in which the ohmic contact junction is arranged in a region other than directly below the surface electrode, when the chip size of the light emitting element is small, A surface electrode having a complicated shape such as an electrode extended linearly results in an increase in the surface electrode area, and the light extraction efficiency decreases.

  An object of the present invention is to provide a semiconductor light emitting device that solves the above-described problems and can improve the light extraction efficiency.

  In order to solve the above problems, the present invention is configured as follows.

A first aspect of the present invention includes a group III-V compound semiconductor layer having a light emitting layer, and a light extraction surface is formed on the first main surface side of the group III-V compound semiconductor layer, A reflective metal film that reflects light from the light emitting layer to the light extraction surface side is formed on the main surface side, and the III-V compound semiconductor layer and the support substrate are bonded via the reflective metal film. A surface electrode is formed on the first main surface of the group III-V compound semiconductor layer, and an ohmic contact junction is formed on a part of the surface of the reflective metal film on the group III-V compound semiconductor layer side. In the semiconductor light emitting device disposed in a region other than directly under the surface electrode, the semiconductor light emitting device has a square shape with one side of 320 μm or less, the surface electrode has a polygonal shape or a round shape, and the outer periphery of the surface electrode. Is 235 μm or more and 700 μm or less in length, The ohmic contact junction is disposed on the outer peripheral side of the semiconductor light emitting element, and when viewed from the surface electrode side, the ohmic contact junction is formed so as to surround the surface electrode, In addition, the semiconductor light emitting device is characterized in that the distance from each position of the outer edge portion of the surface electrode to the nearest ohmic contact junction is equal.

According to a second aspect of the present invention, in the semiconductor light emitting device of the first aspect, a transparent dielectric film is provided between the III-V compound semiconductor layer and the reflective metal film, The ohmic contact junction is formed in part through the transparent dielectric film.

According to a third aspect of the present invention, in the semiconductor light emitting device of the first aspect or the second aspect, the surface of the III-V group compound semiconductor layer serving as the light extraction surface has an uneven shape with a height of 100 nm or more. is there.

According to a fourth aspect of the present invention, in the semiconductor light emitting device according to any one of the first to third aspects, the ohmic contact junction is a polygonal shape or a round shape similar to the polygonal shape or the round shape of the surface electrode. When the ohmic contact junction is viewed from the surface electrode side, it is provided concentrically with the surface electrode.

  According to a fifth aspect of the present invention, in the semiconductor light emitting device of the third aspect or the fourth aspect, the light extraction surface having the concavo-convex shape is covered with a transparent film.

  According to the present invention, it is possible to effectively increase the light extraction efficiency for a semiconductor light emitting device having a small chip size.

  Hereinafter, an embodiment of a semiconductor light emitting device according to the present invention will be described.

The semiconductor light emitting device of this embodiment includes a group III-V compound semiconductor layer having a light emitting layer, and a light extraction surface is formed on the first main surface side of the group III-V compound semiconductor layer. A reflective metal film that reflects light from the light emitting layer to the light extraction surface side is formed on the main surface side, and the III-V compound semiconductor layer and the support substrate are bonded via the reflective metal film. Yes. A back electrode is formed on the support substrate.
The metal reflecting film (at least the second main surface side metal reflecting film) is a metal having a reflectance of 80% or more with respect to the emission wavelength, specifically, any one of Au, Ag, Al, or It is preferable to consist of the alloy.
In order to increase the light extraction efficiency, it is preferable that the light extraction surface has a concavo-convex shape having a surface height (maximum height which is surface roughness) of 100 nm or more.

A surface electrode is formed on the first main surface of the III-V compound semiconductor layer, and an ohmic for reducing contact resistance on a part of the surface of the reflective metal film on the III-V compound semiconductor layer side The contact bonding portion is disposed in a region other than directly below the surface electrode. That is, the ohmic contact junction and the surface electrode have a current confinement structure arranged so as not to overlap each other when viewed from the light extraction surface side.
In the present embodiment, a transparent dielectric film made of a material transparent to the light emitted from the light emitting layer is provided between the III-V compound semiconductor layer and the reflective metal film, and the transparent dielectric The ohmic contact junction is formed through a part of the film through the transparent dielectric film.
The film thickness of the transparent dielectric film is preferably (2 × λ) / (4 × n) or more when the emission wavelength λ and the refractive index of the transparent dielectric film are n. For example, SiO ₂ or SiN is preferably used as the material for the transparent dielectric film.

  The chip size of the semiconductor light emitting element is a quadrangular shape with one side of 320 μm or less, and the surface electrode has a quadrangular shape such as a quadrangular shape or a pentagonal shape, or a round shape such as a circular shape or an elliptical shape. That is, the surface electrode of the present embodiment has a complicated shape such as a surface electrode (for example, surface electrode 111, FIG. 121) instead of a simple polygonal shape (for example, the rectangular surface electrode 13 in FIG. 7) or a round shape (for example, the circular surface electrode 31 in FIG. 8). In other words, the shape of the surface electrode has a small unity shape without a linearly extending portion. The length of the outer periphery of the surface electrode is not less than 235 μm and not more than 700 μm. Note that the same effect can be obtained even when the shape of the surface electrode is such that the square corner is smoothly chamfered with a curved surface or a straight line as in the surface electrode 41 of FIG. 9, for example. On the surface electrode, an electrode pad having the same shape and size as the surface electrode is usually provided.

The ohmic contact junction is arranged on the outer peripheral side of the semiconductor light emitting device, and when viewed from the surface electrode side, the ohmic contact junction surrounds the surface electrode, so that the ohmic contact junction surrounds the surface electrode. And the distance from each position of the outer edge portion of the surface electrode to the nearest ohmic contact junction (for example, see the distance (shortest distance) L in FIG. 7) is equal.

Specifically, the surface electrode is formed at the center of the first main surface of the III-V compound semiconductor layer,
The ohmic contact junction is formed in a polygonal shape (for example, a square shape) or a round shape (for example, a circular shape), and the ohmic contact junction surface surrounds the surface electrode when viewed from the surface electrode side. It is provided in a concentric arrangement such as a polygonal shape or a round line shape similar to the electrode.

Note that the ohmic contact junction may be provided so as to surround the surface electrode when viewed from the surface electrode side, and the ohmic contact junction has a single closed shape such as a polygonal shape or a round linear shape. It is not limited to that, but may be arranged in a polygonal shape or a round shape as a whole so that a plurality of divided lines or the like surround the surface electrode. Alternatively, the ohmic contact junction does not surround the entire outer periphery of the surface electrode. For example, a rectangular surface electrode is arranged near one side of the light emitting element chip instead of the central portion of the light emitting element chip. These three sides may be surrounded by an ohmic contact junction in a U-shape.
In addition, although the arrangement is made such that the distance from each position of the outer edge portion of the surface electrode to the nearest ohmic contact junction is equal, the arrangement may be such that there are some portions where the distance is not equal.

When a forward voltage is applied to the semiconductor light emitting device, a current flows from the surface electrode through the ohmic contact junction to the support substrate. At that time, light is emitted from the light emitting layer between the surface electrode and the ohmic contact junction. The emitted light is extracted to the outside of the light emitting element from the light extraction surface or the side surface of the III-V compound semiconductor layer.

  When the chip size of the light-emitting element is large, the surface electrode with a complicated shape that extends linearly from a central part such as a circle has good current dispersion and does not have much light absorption or light shielding. Excellent surface electrode shape. However, recently, a light-emitting element having a small chip size has been manufactured, and when the chip size is smaller than 320 μm on one side, the surface electrode having a complicated shape having a linearly extending portion is formed on the top surface of the light-emitting element chip. The ratio of the area of the surface electrode in the area is increased, and the increase in the amount of light absorption becomes a problem rather than the improvement in current dispersibility, and the light extraction efficiency is lowered.

Therefore, in the present embodiment, the surface electrode has a simple polygonal shape or a round shape, and when viewed from the surface electrode side, the ohmic contact junction is surrounded by the surface electrode. And it arrange | positions on the outer peripheral side of a semiconductor light-emitting device so that it may keep distance as much as possible from a surface electrode.
This is because the light extraction efficiency depends on the distance between the ohmic contact junction and the surface electrode (particularly, the horizontal distance between the ohmic contact junction and the surface electrode when the ohmic contact junction is viewed from the surface electrode side). The light output increases as the distance changes greatly and the distance increases. When the surface electrode becomes large, the above-mentioned distance is inevitably reduced, so that the light emission output is also reduced.

The surface electrode (or electrode pad) needs to have a minimum length and dimension of 75 μm or more so that a straight line passing through the center of the surface electrode crosses the surface electrode in order to enable wire bonding with a high yield. The shape of the surface electrode (or electrode pad) that can secure the minimum length of 75 μm and that can shorten the outer peripheral length is the case of a circular shape with a diameter of 75 μm, and the circular outer peripheral length with a diameter of 75 μm is 235 μm. Therefore, the outer peripheral length of the surface electrode is preferably 235 μm or more.
On the other hand, when one side of the chip size of the light emitting element is smaller than 320 μm, if the outer circumference of a simple round or polygonal surface electrode is longer than 700 μm, the light extraction efficiency decreases due to light absorption of the surface electrode. As a result, the light emission output is significantly reduced (see FIGS. 11 and 12). Therefore, the outer peripheral length of the surface electrode is preferably 700 μm or less.
When one side of the chip is larger than 320 μm, it is a surface electrode having a portion extending linearly from a simple round or square surface electrode (electrode pad) and spread by spreading the current in the chip However, the light emission output is improved. Conversely, for a relatively small chip with one side of 320 μm or less, extending the linear electrode from a simple round or polygonal surface electrode (electrode pad) has the effect of spreading the current over the entire chip. As described above, it is considered that the light absorption factor acts so much that the light emission output cannot be increased (see FIG. 13).

  Next, examples of the present invention will be described.

Example 1
FIG. 7 shows the semiconductor light emitting device of Example 1. 1 to 6 show respective steps of the method for manufacturing the semiconductor light emitting device of the first embodiment. 1 to 6 show a situation in which two light emitting elements 20 are manufactured side by side for simplification of the drawings.

  First, an epitaxial wafer for red LEDs having a light emission wavelength of about 630 nm having the structure shown in FIG. 1 was produced. The epitaxial growth method, epitaxial structure, electrode forming method, and LED element manufacturing method are as follows.

In the epitaxial growth, an undoped (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P etching stop layer 2 and an n-type (Si-doped) GaAs contact layer are formed on the n-type GaAs substrate 1 using the MOVPE method. 3, n-type (Si doped) (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layer 4, undoped (Al _0.1 Ga _0.9 ) _0.5 In _0.5 P activity Layer (light emitting layer) 5, p-type (Mg doped) (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layer 6, and p-type (Mg doped) GaP contact layer 7 are formed by MOVPE method. The layers were grown in order.
The growth temperature in MOVPE growth was 650 ° C., the growth pressure was 50 Torr (about 6666 Pa), the growth rate of each layer was 0.3 to 1.0 nm / sec, and the V / III ratio was about 200. Incidentally, the V / III ratio mentioned here is a ratio (quotient) when the denominator is the number of moles of a group III material such as TMGa or TMAl and the numerator is the number of moles of a group V material such as AsH ₃ or PH _3. Point to.
The raw material used in the MOVPE growth, for example, trimethyl gallium (TMGa), or triethylgallium (TEGa), trimethylaluminum (TMAl), and organometallic birds such as trimethyl indium (TMIn), arsine _(AsH 3), phosphine _(PH 3) A hydride gas such as was used. Disilane (Si ₂ H ₆ ) was used as an additive material for the conductivity type determining impurity of the n-type semiconductor layer. Moreover, biscyclopentadienyl magnesium (Cp ₂ Mg) was used as an additive material for the conductivity determining impurity of the p-type semiconductor layer.
In addition, hydrogen selenide (H ₂ Se), monosilane (SiH ₄ ), diethyl tellurium (DETe), or dimethyl tellurium (DMTe) can also be used as an additive material for the conductivity determining impurity of the n-type layer. In addition, dimethyl zinc (DMZn) and diethyl zinc (DEZn) can also be used as a p-type additive material for the p-type layer.

Further, after the LED epitaxial wafer is unloaded from the MOCVD apparatus, a SiO ₂ film 8 as a transparent dielectric film is formed on the surface of the p-type GaP contact layer 7 by a plasma CVD apparatus, and a resist, a mask aligner, etc. Using a general photolithography technique, an opening (a square linear opening) is formed in the SiO ₂ film 8 with a hydrofluoric acid-based etching solution, and a linear square is formed in the opening by vacuum deposition. An ohmic contact junction 9 was formed (FIG. 2). 2A is a top view, and FIG. 2B is a cross-sectional view taken along the line 2B-2B in FIG.
An AuZn (gold / zinc) alloy was used for the ohmic contact junction 9. Further, the ohmic contact junction 9 was disposed so as to be in a region other than directly below the surface electrode 13 to be formed later.

Next, an Al (aluminum) layer, a Ti (titanium) layer, and an Au (gold) layer were sequentially deposited as the reflective metal film 10 on the above-described LED epitaxial wafer with an ohmic contact junction (FIG. 3). The Al layer is a reflection layer (reflection film), Ti is a diffusion barrier layer, and Au is a bonding layer.
On the other hand, a Ti (titanium) layer, a Pt (platinum) layer, and an Au (gold) layer were sequentially deposited on the surface of the conductive Si substrate 11 prepared as a support substrate to form a metal adhesion layer 12 (FIG. 3). ). The Ti layer is an ohmic contact metal layer, Pt is a diffusion barrier layer, and Au is a bonding layer.
The Au bonding layer on the surface of the LED epitaxial wafer produced as described above is bonded to the Au bonding layer on the surface of the Si substrate 11 (FIG. 3). Bonding is performed at a pressure of 0.01 Torr (
About 1.33 Pa) With a load of 30 kgf / cm ² in an atmosphere, the temperature is 350 ° C. and 3
This was done by holding for 0 minutes.

Next, the GaAs substrate 1 of the LED epitaxial wafer bonded to the Si substrate 11 is removed by etching with a mixed solution of ammonia water and hydrogen peroxide solution, and undoped (Al _0.7).
Ga _0.3 ) _0.5 In _0.5 P etching stop layer 2 was exposed. Further, the etching stop layer 2 was removed with hydrochloric acid to expose the n-type GaAs contact layer 3 (FIG. 4).

Next, a general photolithography technique such as a resist or a mask aligner was used on the surface of the n-type GaAs contact layer 3 to form an n-side surface electrode 13 made of a square having a side of 100 μm by a vacuum deposition method. The surface electrode 13 was formed by sequentially depositing an AuGe (gold-germanium alloy) layer, a Ti (titanium) layer, and an Au (gold) layer. After the formation of the surface electrode 13, the GaAs contact layer 3 other than directly below the surface electrode 13 is removed by etching using an etchant composed of a mixture of sulfuric acid, hydrogen peroxide and water, using the formed surface electrode 13 as a mask, The n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 4 was exposed by selective etching (FIG. 5).

Next, patterning with a period of 1.0 μm to 3.0 μm is performed on the n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layer 4 to be the light extraction surface 4a by using a photolithography technique. Then, an uneven shape was formed on the surface of the n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 4 by wet etching (FIG. 6).
Further, patterning for element isolation was performed using a photolithography technique, and element isolation was performed by removing the surface from the n-type cladding layer 4 to the p-type GaP contact layer 7 by wet etching (FIG. 6). ).

Next, after forming a back electrode 14 made of a Ti (titanium) layer and an Au (gold) layer on the back surface of the Si substrate 11 by vacuum deposition, alloying of the electrode is performed in a nitrogen gas atmosphere. It was performed by heating to 400 ° C. and heat treating for 5 minutes.
Further, a surface electrode pad 15 made of a Ti (titanium) layer and an Au (gold) layer for wire bonding was formed on the surface electrode 13 by photolithography and vacuum deposition.
Thereafter, the electrode substrate with the electrode formed as described above was cut using a dicing apparatus to produce an LED bare chip having a chip size of 300 μm square (FIG. 7).
Furthermore, the LED bare chip was mounted on a TO-18 stem (die bonding), and then wire bonding was performed on the mounted LED bare chip to produce an LED element.

(Example 2, Example 3)
As Example 2, a replaceable red light emitting device 30 having an emission wavelength near 630 nm and having the structure shown in the top view of FIG. Further, as Example 3, a repositionable red light emitting device 40 having an emission wavelength near 630 nm and having the structure shown in the top view of FIG. In Example 2 and Example 3, process steps such as an epitaxial growth method, an epitaxial layer thickness, an epitaxial layer structure, a reflective metal film, a method of attaching to a support substrate, an etching method, and an LED element manufacturing method are basically Same as Example 1 above.
The difference from the first embodiment is that in the second embodiment, as shown in FIG. 8, the surface electrode 31 has a circular shape, and surrounds the circular surface electrode 31 as viewed from the surface electrode 31 side. The point is that the ohmic contact junctions 32 are provided in a concentric arrangement. In Example 3, as shown in FIG. 9, the surface electrode 41 has a shape in which a square corner portion is smoothly rounded on the R surface, and surrounds the surface electrode 31 when viewed from the surface electrode 41 side. 41, linear ohmic contact junctions 42 having a similar shape to that of 41 are provided in a concentric arrangement.

(Comparative Example 1 and Comparative Example 2)
As Comparative Example 1, a repositionable red light emitting device 110 having an emission wavelength near 630 nm and having the structure shown in the top view of FIG. In addition, as Comparative Example 2, a repositionable red light emitting device 120 having a structure having the structure shown in the top view of FIG. In Comparative Example 1 and Comparative Example 2, process steps such as epitaxial growth method, epitaxial layer thickness, epitaxial layer structure, reflective metal film, support substrate replacement method, etching method, and LED element manufacturing method are basically Same as Example 1 above.
The difference from Example 1 is that, in Comparative Example 1, as shown in FIG. 10 (a), the surface electrode 111 has a circular central portion (portion where the electrode pad is formed) (diameter 100 μm). The linear electrode extends radially from the center of the circle, and the linear ohmic contact junction 112 is provided so as to surround the linear electrode of the surface electrode 111 when viewed from the surface electrode 111 side. It is. Moreover, in the comparative example 2, as shown in FIG.10 (b), the surface electrode 121 is circular (diameter 100 micrometers) in the center part (part in which an electrode pad is formed), and is radial from this circular center part. The linear electrode extends and a part of the linear electrode is further branched to the left and right at the tip, and the linear electrode is formed so as to surround the linear electrode of the surface electrode 121 when viewed from the surface electrode 121 side. The ohmic contact junction 122 is provided.

After the LED element of the example produced as described above was molded with an epoxy resin, a current of 20 mA was applied to examine the LED characteristics.
FIG. 11 shows the relationship between the outer peripheral length of the square surface electrode (electrode pad) and the light emission output in the structure of Example 1 shown in FIG. FIG. 12 shows the relationship between the outer peripheral length of the circular surface electrode (electrode pad) and the light emission output in the structure of Example 2 shown in FIG.
From FIG. 11 and FIG. 12, when the length of the outer periphery of the surface electrode is longer than 700 μm, the light emission output is significantly reduced. This is because the area of the surface electrode increases and the absorption factor in the light emitting element increases. Moreover, the same effect as Example 1 was confirmed also in the surface electrode shape of Example 3 shown in FIG.

  Moreover, also about the comparative example 1 and the comparative example 2 which are shown to Fig.10 (a), (b), resin mold was carried out similarly to the Example, 20 mA electricity supply was carried out, and the light emission output was evaluated. As a result, in Comparative Example 1 and Comparative Example 2, the light emission outputs were 8.7 mW and 9.5 mW, respectively, which were lower values than in the example. This is because, in the case of a relatively small chip having a side of 320 μm or less, if the linear electrode is extended from the surface electrode (electrode pad), the light absorption factor acts more than the effect of spreading the current over the entire chip. Therefore, it is considered that the light emission output does not increase.

Next, the chip size of the light-emitting element 40 of Example 3 shown in FIG. 9 is 200 μm to 500 μm.
It is manufactured up to μm (manufactured while maintaining a pattern shape similar to the surface electrode 41 and the ohmic contact bonding portion 42 shown in FIG. 9), and the manufactured light emitting element 40 of Example 3 is molded with an epoxy resin, and then 20 mA. The light emission output was measured by applying current. Similarly, the light emitting device 120 of Comparative Example 2 shown in FIG. 10B is manufactured by changing the chip size from 200 μm to 500 μm (a pattern similar to the surface electrode 121 and the ohmic contact junction 122 shown in FIG. 10B). The shape was kept, and the light emitting device 120 of Comparative Example 2 thus manufactured was molded with an epoxy resin, and then 20 mA current was applied to measure the light emission output.
FIG. 13 shows the measurement results. As shown in FIG. 13, when the length of one side (chip size) of the light emitting element chip is 320 μm or less, the structure of the light emitting element of Example 3 according to the present invention has a light emission output higher than that of the light emitting element of Comparative Example 2. It was confirmed that it was large and effective.

Example 4
In Example 4, in the light emitting device of the above example, the light extraction surface 4a formed in the concavo-convex shape was covered with the transparent films 17 and 18.
First, by repeatedly applying to the uneven light extraction surface 4a, the concave portion of the light extraction surface 4a was filled, and the transparent film 17 having a corrugated surface corresponding to the uneven shape of the light extraction surface 4a was formed. Further, a transparent film 18 having a flat surface was formed on the transparent film 17 by sputtering. By forming the transparent film 18 by sputtering, the transparent film 18 can be formed with good crystallinity, and entry of moisture and the like from the outside can be prevented. In the present invention, since the surface electrode is a simple polygonal shape or a round shape, coating and sputtering for forming the transparent films 17 and 18 can be easily performed.
By covering the uneven light extraction surface 4a with the transparent films 17 and 18, the uneven portion of the light extraction surface 4a can be protected. Further, by making the refractive index of the transparent film 17 smaller than the refractive index of the semiconductor layer 4 having the light extraction surface 4a (about 3.5 to 3.6), reflection on the light extraction surface 4a is prevented. Can be suppressed. Furthermore, it is preferable that the refractive index of the transparent film 18 be smaller than the refractive index of the transparent film 17, whereby reflection at the interface between the transparent film 17 and the transparent film 18 can be suppressed. Further, since the surface of the transparent film 17 has a corrugated curved surface, an improvement in light extraction due to the lens effect can be expected.
The transparent films 17 and 18 may use either a conductive material or an insulating material. Specifically, _ITO, etc. SiO 2, _Si 3 _{N 4} and the like. Further, for example, the transparent film 17 on the semiconductor layer 4 side may be a conductive material, and the transparent film 18 on the surface side may be an insulating material. Further, the transparent film 18 may be omitted and only the transparent film 17 may be used. Note that the materials and manufacturing methods used for the transparent films 17 and 18, the order of forming the transparent films 17 and 18 in the light emitting element manufacturing process, and the like are appropriately determined in consideration of the characteristics, productivity, cost, and the like of the light emitting elements.

(Other examples)
In the above embodiment, the Si substrate 11 is used as the support substrate. However, any substrate other than the Si substrate can be used as long as the support substrate can withstand the light emitting element manufacturing process. Specific examples include a Ge substrate, a GaAs substrate, a GaP substrate, and other metal substrates.
In the above embodiment, the active layer (light emitting layer) 5 is a bulk layer, but the effect is the same in a multiple quantum well or the like. Further, in the above embodiment, a red light emitting element having an emission wavelength near 630 nm has been described. However, the present invention provides an effect of improving the light emission output without depending on the light emission wavelength of the LED.
In the above embodiment, the light extraction surface 4a side is an n-type doping layer, but the same effect can be obtained even if the n-type layer and the p-type layer are reversed.

7 is a cross-sectional view showing a manufacturing step of the semiconductor light-emitting element of Example 1. FIG. FIGS. 2A and 2B are cross-sectional views taken along the line 2B-2B of FIG. 2A, respectively, illustrating a manufacturing process of the semiconductor light emitting device of Example 1. FIG. 7 is a cross-sectional view showing a manufacturing step of the semiconductor light-emitting element of Example 1. FIG. 7 is a cross-sectional view showing a manufacturing step of the semiconductor light-emitting element of Example 1. FIG. FIGS. 5A and 5B show a manufacturing process of the semiconductor light emitting device of Example 1, in which FIG. 5A is a top view and FIG. 5B is a cross-sectional view taken along 5B-5B in FIG. The manufacturing process of the semiconductor light emitting element of Example 1 is shown, FIG. 6A is a top view and FIG. 6B is a 6B-6B cross-sectional view of FIG. The semiconductor light-emitting device of Example 1 is shown, FIG. 7A is a top view, and FIG. 7B is a 7B-7B cross-sectional view of FIG. 6 is a top view of a semiconductor light emitting device of Example 2. FIG. 6 is a top view of a semiconductor light emitting device of Example 3. FIG. It is a top view of the semiconductor light emitting element of a comparative example. In the structure of Example 1, it is a graph which shows the relationship between the outer periphery length of a surface electrode, and light emission output. In the structure of Example 2, it is a graph which shows the relationship between the outer periphery length of a surface electrode, and light emission output. 4 is a graph showing the relationship between the length of one side of a semiconductor light emitting element and the light emission output in the semiconductor light emitting elements of Examples and Comparative Examples. 6 is a partial enlarged cross-sectional view of a light extraction surface in a semiconductor light emitting element of Example 4. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Growth GaAs substrate 2 AlGaInP etching stop layer 3 n-type GaAs contact layer 4 n-type AlGaInP clad layer 4a Light extraction surface 5 AlGaInP active layer 6 p-type AlGaInP clad layer 7 p-type GaP contact layer 8 SiO ₂ film 9 ohmic contact junction Part 10 Reflective metal layer 11 Si substrate 12 Metal adhesion layer 13 Surface electrode 14 Back electrode 15 Electrode pad 17 Transparent film 18 Transparent film 20 Light emitting element 30 Light emitting element 31 Surface electrode 32 Ohmic contact junction 40 Light emitting element 41 Surface electrode 42 Ohmic contact Junction

Claims (5)

A III-V group compound semiconductor layer having a light emitting layer, wherein a light extraction surface is formed on a first main surface side of the III-V group compound semiconductor layer, and a second main surface side is formed from the light emitting layer; A reflective metal film that reflects the light of the light to the light extraction surface side is formed, and the III-V compound semiconductor layer and the support substrate are joined via the reflective metal film, and the III-V compound semiconductor A surface electrode is formed on the first main surface of the layer, and an ohmic contact junction is arranged in a region other than directly below the surface electrode on a part of the surface of the reflective metal film on the III-V compound semiconductor layer side In the semiconductor light emitting device made,
The semiconductor light emitting device has a square shape with one side of 320 μm or less,
The surface electrode has a polygonal shape or a round shape, and the length of the outer periphery of the surface electrode is 235 μm or more and 700 μm or less,
The ohmic contact junction is disposed on the outer peripheral side of the semiconductor light emitting element, and when viewed from the surface electrode side, the ohmic contact junction is formed so as to surround the surface electrode, The semiconductor light emitting device is characterized in that the distance from each position of the outer edge portion of the surface electrode to the nearest ohmic contact junction is equal. 2. The semiconductor light emitting device according to claim 1, wherein a transparent dielectric film is provided between the III-V compound semiconductor layer and the reflective metal film, and the transparent dielectric film is formed on a part of the transparent dielectric film. A semiconductor light emitting device, wherein the ohmic contact junction is formed therethrough. 3. The semiconductor light emitting device according to claim 1, wherein the surface of the III-V compound semiconductor layer serving as the light extraction surface has an uneven shape with a height of 100 nm or more.   4. The semiconductor light emitting element according to claim 1, wherein the ohmic contact junction is formed in a polygonal shape or a round shape similar to the polygonal shape or the round shape of the surface electrode, and the A semiconductor light emitting device, which is provided concentrically with the surface electrode when the ohmic contact junction is viewed from the surface electrode side.   5. The semiconductor light emitting device according to claim 3, wherein the light extraction surface having the concavo-convex shape is covered with a transparent film.