JP5304563B2 - Group III nitride semiconductor light emitting device - Google Patents

Description

  The present invention relates to a group III nitride semiconductor light emitting device in which a growth substrate is removed by a substrate lift-off method and bonded to a support.

  A sapphire substrate is generally used as a growth substrate for a group III nitride semiconductor. However, sapphire has problems with conductivity and thermal conductivity, and it is not easy to process without a clear cleavage plane. Therefore, as a technique for solving these problems, a technique (substrate lift-off) has been developed in which a growth substrate is removed after a group III nitride semiconductor is grown on the growth substrate.

  One such technique is the laser lift-off method. This is because after the group III nitride semiconductor layer and the support substrate are joined, the interface between the growth substrate and the group III nitride semiconductor is irradiated with a laser to decompose the group III nitride semiconductor layer and remove the growth substrate. It is a method to do. As another technique, a layer that can be dissolved in a chemical solution is introduced into a layer close to the growth substrate of the group III nitride semiconductor layer, the group III nitride semiconductor layer and the support substrate are joined, and then the above-described method is performed using a desired chemical solution. A method of removing a growth substrate by dissolving a layer that can be dissolved in a chemical solution (chemical lift-off method) is also known.

  Patent Document 1 discloses a technique for improving light extraction efficiency in a group III nitride semiconductor light-emitting device in which such a growth substrate is removed and bonded to a support substrate. In the light emitting device described in Patent Document 1, a light reflecting recess having a depth reaching the n-type layer from the surface of the p-type layer bonded to the p-electrode is provided, and as the p-type layer moves toward the n-type layer. The side surface of the recess is inclined so that the cross-sectional area in the element surface direction decreases. The reflection recesses reflect light confined in the vicinity of the active layer and propagating in the element surface direction to the n-type layer side, thereby improving light extraction efficiency.

2008-205005

  However, even if a light reflecting recess is provided as in Patent Document 1, a part of the light reflected to the n-type layer side by the light reflecting recess is bonded to the n-type layer n electrode. The light extraction efficiency is not sufficiently improved because the light is reflected on the surface on the light-receiving side and returns to the inside of the element.

  It is also conceivable to improve the light extraction efficiency by reducing the area occupied by the n-electrode formed on the surface of the n-type layer. However, in that case, the current is not sufficiently diffused in the direction of the element surface, the uniformity of light emission is impaired, and the light emission efficiency is greatly reduced when driven at a high current density.

  Accordingly, an object of the present invention is to provide a group III nitride semiconductor light-emitting device having improved light extraction efficiency without impairing the uniformity of light emission.

The first invention includes a conductive support, a p-electrode positioned on the support, a p-type layer made of a group III nitride semiconductor, an active layer, and an n-type layer, which are sequentially positioned on the p-electrode, In a group III nitride semiconductor light emitting device having an n-electrode positioned on an n-type layer, a groove formed in a wiring pattern having a depth reaching the n-type layer from the p-electrode side surface of the p-type layer And an auxiliary electrode formed in a wiring pattern that is in contact with the n-type layer at the bottom surface of the groove and not in contact with the side surface of the groove, and the auxiliary electrode and the light-transmitting insulation covering the bottom and side surfaces of the groove A group III nitride semiconductor light-emitting device, wherein the area of the n-electrode is smaller than the area of the auxiliary electrode .

Here, the group III nitride semiconductor is a semiconductor represented by the general formula Al _x Ga _y In _z N (x + y + z = 1, 0 ≦ x, y, z ≦ 1), and a part of Al, Ga, and In Is replaced with other Group B elements (Group 13 elements) B or Tl, and part of N is replaced with other Group 5B elements (Group 15 elements) P, As, Sb, Bi. Including replacements. More generally, GaN, InGaN, AlGaN, or AlGaInN containing at least Ga is shown. Usually, Si is used as an n-type impurity and Mg is used as a p-type impurity.

  The n electrode may be only a circular or square pad part, or may be composed of a pad part and a wiring part. The n-electrode pattern may be any pattern, but a symmetrical pattern is desirable to improve the uniformity of light emission. For example, there are a pattern in which a wiring portion extends radially from a pad portion provided in the center, a pattern in which a wiring portion is a rectangle, and two pad portions are provided at the vertex positions of the rectangle.

The groove and the auxiliary electrode may be an arbitrary wiring pattern, but a symmetrical wiring pattern is desirable in order to improve the uniformity of light emission. For example, a grid pattern, a stripe pattern, a radial pattern, a combined pattern of these, and the like. The pattern of the groove and the pattern of the auxiliary electrode do not need to match, and the pattern of the auxiliary electrode may be a part of the pattern of the groove. Further, it is desirable that a part of the auxiliary electrode and a part or all of the n-electrode are opposed to each other in a direction perpendicular to the element surface, and the opposed region is desirably as wide as possible. This is because conduction between the auxiliary electrode and the n electrode is facilitated, and current diffusion in the element surface direction by the auxiliary electrode becomes easier. In addition, since light from the active layer directly under the n electrode is shielded by the n electrode, it is advantageous to reduce the loss by forming a groove and an auxiliary electrode in a region facing the n electrode so as not to emit light. That's why. In particular, it is desirable to provide a part of the auxiliary electrode with the same area and shape as the pad portion at a position facing the pad portion of the n electrode in the direction perpendicular to the element surface. In addition, a part of the groove and the auxiliary electrode may be a wiring pattern that surrounds the outside of the light emitting region. Here, the light-emitting region is a region that emits light when a voltage is applied to the light-emitting element, and substantially coincides with a region where the active layer formation region and the p-electrode formation region overlap. If a part of the groove and the auxiliary electrode has such a pattern, the light emitted from the side surface of the element can be reflected to the n-type layer side by the side surface of the groove. Although the emission from the upper surface decreases and the light emitted from the side surface of the element is generally not effectively used, a substantial increase in efficiency can be achieved.

The area of the auxiliary electrode is wider than the area of the n electrode . This is because by reducing the area of the n-electrode and increasing the area of the auxiliary electrode, it is possible to improve the light extraction efficiency while maintaining the uniformity of light emission. In particular, it is preferable that the area of the n electrode is 1 to 10% of the element area and the area of the auxiliary electrode is 4 to 16% of the element area because the light extraction efficiency can be further improved.

  Further, the n electrode and the auxiliary electrode may be partially continuous by a structure such that a partial region of the groove penetrates the n-type layer. However, it is not desirable to widen the continuous area. This is because the area where the auxiliary electrode comes into contact with the + c plane of the n-type layer of the group III nitride semiconductor is reduced, and the effect of diffusing current in the element plane direction is reduced.

  It is desirable that the side surface of the groove be inclined so that the cross-sectional area in the element surface direction of the groove decreases toward the n-type layer side. This is because light propagating in the element surface direction can be reflected to the n-type layer side by the side surface of the groove, and the light extraction efficiency can be further improved. The angle formed by the side surface of the groove with respect to the element surface is preferably 30 to 85 °. This is because the light extraction efficiency cannot be sufficiently improved at an angle of less than 30 ° or an angle of greater than 85 °. A more desirable angle is 40 to 80 °.

  As the material of the auxiliary electrode, any material conventionally known as an n-electrode material for making contact with the + c plane (Ga polar plane) of the n-type layer of the group III nitride semiconductor can be used. For example, materials such as V / Ni, Ti / Al, V / Au, Ti / Au, and Ni / Au can be used for the auxiliary electrode. The material of the n-electrode can be the same as the material of the auxiliary electrode, but other materials that can make good contact with the -c plane (N-polar plane) of the n-type layer of the group III nitride semiconductor Materials may be used.

  It is desirable to improve the light extraction efficiency by providing fine irregularities on the n-type layer surface by wet etching with an aqueous solution of KOH, NaOH, TMAH (tetramethylammonium hydroxide), phosphoric acid or the like. In the case of providing fine unevenness, it is desirable that the n electrode formation region is not provided with fine unevenness and remains flat. This is to prevent light from being reflected and attenuated between the n-electrode and the fine irregularities, thereby deteriorating the light extraction efficiency.

The insulating film is provided to prevent current leakage and short circuit. Any material can be used for the insulating film as long as the material has translucency and insulating properties with respect to the emission wavelength of the light emitting element. For example, SiO ₂ , Al ₂ O ₃ , Si ₃ N ₄ , TiO ₂ can be used. Etc. can be used. It is desirable to provide a highly reflective layer on the side surface and bottom surface of the groove via an insulating film. Further, the p electrode made of a highly reflective material may be the highly reflective layer. Alternatively, a dielectric multilayer film may be provided on the side surface and bottom surface of the groove via an insulating film, or the insulating film itself may be a dielectric multilayer film to increase the reflectivity.

  The group III nitride semiconductor growth substrate is generally sapphire, but other materials such as SiC, ZnO, and spinel can be used. In addition, a substrate such as Si, Ge, GaAs, Cu, or Cu-W can be used as the support, and the p electrode is attached on the support by bonding the p electrode and the support through a metal layer. Can be formed. As the metal layer, a metal eutectic layer such as an Au—Sn layer, an Au—Si layer, an Ag—Sn—Cu layer, or a Sn—Bi layer can be used, and an Au layer, a Sn layer, a Cu layer, or the like is used. You can also. Further, a metal layer such as Cu may be formed directly on the p-electrode by plating, sputtering, or the like to form a support.

A second aspect of the invention is Oite to the first invention, the side surfaces of the groove has an inclined sectional area of the element surface direction of the groove decreases toward the n-type layer side, III-nitride, characterized in that It is a semiconductor light emitting device.

A third invention is a group III nitride according to the first invention or the second invention, wherein at least part of the auxiliary electrode is formed at a position facing part or all of the n electrode. A semiconductor light emitting device.

A fourth invention is a group III nitride semiconductor light emitting device according to the first to third inventions, wherein the groove and part of the auxiliary electrode have an outer peripheral wiring portion surrounding the outside of the light emitting region It is.

According to a fifth invention, in the first to fourth inventions, the auxiliary electrode is made of V / Al, Ti / Al, V / Au, Ti / Au, or Ni / Au. This is a nitride semiconductor light emitting device.

  In the first invention, an auxiliary electrode is provided which is electrically connected to the n electrode and assists current diffusion in the element surface direction. Since the auxiliary electrode is in contact with the + c plane of the n-type layer of the group III nitride semiconductor which is the bottom surface of the groove, the contact resistance is low. Therefore, the current can be efficiently diffused in the element surface direction by the auxiliary electrode, and the uniformity of light emission can be improved. As a result, it is less necessary to spread the current in the plane direction by the n electrode, the area occupied by the n electrode can be reduced, the obstruction of light extraction due to the presence of the n electrode is reduced, and the light extraction efficiency is improved. Can be improved.

Further, without impairing the uniformity of light emission, further can reduce the inhibition of light extraction due to the presence of the n-electrode, it is possible to improve the light extraction efficiency.

Further, to improve the diffusion of the current to the element surface direction by the auxiliary electrode, it is possible to enhance the uniformity of light emission.

Further, according to the second invention, the light confined in the surface of the element by the side surface of the groove can be reflected upward, and the light extraction efficiency can be improved.

In addition, according to the third invention, conduction between the n electrode and the auxiliary electrode is facilitated, and the current diffusibility in the element surface direction is improved, so that the uniformity of light emission can be further improved.

In addition, according to the fourth invention, since light emission from the side surface of the element is reduced and radiation from the upper surface of the element is increased, a substantial increase in efficiency can be achieved.

As in the fifth invention, V / Al, Ti / Al, V / Au, Ti / Au, and Ni / Au can be used as the auxiliary electrode material.

FIG. 4 shows a structure of a light-emitting element 100 of Example 1. The figure which showed the pattern of the n electrode. The figure which showed the pattern of the auxiliary electrode. FIG. 10 shows a manufacturing process of the light-emitting element 100. FIG. 10 shows a manufacturing process of the light-emitting element 100. FIG. 10 shows a manufacturing process of the light-emitting element 100. FIG. 10 shows a manufacturing process of the light-emitting element 100. FIG. 10 shows a manufacturing process of the light-emitting element 100. FIG. 10 shows a manufacturing process of the light-emitting element 100. FIG. 10 shows a manufacturing process of the light-emitting element 100. FIG. 10 shows a manufacturing process of the light-emitting element 100. The figure which showed the pattern of the other n electrode and auxiliary electrode. The figure which showed the pattern of the other n electrode and auxiliary electrode. The figure which showed the pattern of the other n electrode and auxiliary electrode. The figure which showed the pattern of the other n electrode and auxiliary electrode.

  Hereinafter, specific examples of the present invention will be described with reference to the drawings. However, the present invention is not limited to the examples.

  FIG. 1 is a cross-sectional view illustrating the structure of the light emitting device 100 of Example 1, and FIG. 2 is a view of the light emitting device 100 as viewed from above. As shown in FIG. 2, the light emitting device 100 is square in a plan view. As shown in FIG. 1, the support 101, the p electrode 103 bonded to the support 101 via the low melting point metal layer 102, and p A p-type layer 104 made of a group III nitride semiconductor, an active layer 105, an n-type layer 106, and an n-electrode 107 formed on the n-type layer 106 are sequentially stacked on the electrode 103.

  As the support 101, a conductive substrate made of Si, GaAs, Cu, Cu—W, or the like can be used. As the low melting point metal layer 102, a metal eutectic layer such as an Au—Sn layer, an Au—Si layer, an Ag—Sn—Cu layer, or a Sn—Bi layer can be used. An Sn layer, a Cu layer, or the like can also be used. The support 101 may be formed by forming a metal layer such as Cu directly on the p electrode 103 by plating, sputtering, or the like, instead of joining the support 101 and the p electrode 103 using the low melting point metal layer 102. Good. The p-electrode 103 is a metal with high light reflectivity and low contact resistance, such as Ag, Rh, Pt, Ru, or an alloy containing these metals as a main component. In addition, Ni, Ni alloy, Au alloy or the like can be used as the material of the p electrode 103, and a composite layer made of a transparent electrode film such as ITO and a highly reflective metal film may be used.

  The p-type layer 104, the active layer 105, and the n-type layer 106 may have any configuration conventionally known as a configuration of a light emitting element. The p-type layer 104 has, for example, a structure in which a p-contact layer doped with Mg made of GaN and a p-cladding layer doped with Mg made of AlGaN are stacked in order from the support 101 side. The active layer 105 has, for example, an MQW structure in which a barrier layer made of GaN and a well layer made of InGaN are repeatedly stacked. The n-type layer 106 has, for example, a structure in which an n-cladding layer made of GaN and an n-type contact layer doped with Si at a high concentration are stacked in order from the active layer 105 side.

  A groove 108 is formed on the surface of the p-type layer 104 on the side where the p-type layer 104 is joined. The groove 108 has a depth that penetrates the p-type layer 104 and the active layer 105 and reaches the n-type layer 106. The side surface of the groove 108 is inclined so that the cross-sectional area in the element surface direction decreases as it goes from the p-type layer 104 to the n-type layer 106, and the bottom surface of the groove 108 is parallel to the element surface.

  The inclination angle of the side surface of the groove 108 is desirably 30 to 85 degrees with respect to the element surface direction, and more desirably 40 to 80 degrees. This is because the light extraction efficiency can be further improved.

The n-type layer 106 is exposed on the bottom surface of the groove 108, and the auxiliary electrode 109 is formed so as to be in contact with the bottom surface of the groove 108 where the n-type layer 106 is exposed and not in contact with the side surface of the groove 108. In addition, an insulating film 110 made of SiO ₂ is formed on the side surface of the groove 108, the bottom surface of the groove 108 where the auxiliary electrode 109 is not formed, and the auxiliary electrode 109. This insulating film 110 is provided in order to prevent a short circuit between the side surface of the trench 108 and the p-electrode 103 and between the auxiliary electrode 109 and the p-type layer 104. As the auxiliary electrode 109, a material conventionally used as an n-electrode material that contacts the + c plane of the n-type layer of the group III nitride semiconductor can be used. For example, materials such as V / Ni, Ti / Al, V / Au, Ti / Au, and Ni / Au can be used.

The insulating film 110 may be made of a material having translucency and insulating properties with respect to the emission wavelength of the light emitting element 100. In addition to SiO ₂ , Al ₂ O ₃ , Si ₃ N ₄ , TiO _2, etc. Can be used.

  A gap is formed between the side surface of the groove 108 and the auxiliary electrode 109 via the insulating film 110, and this gap is filled with the p-electrode 103 made of highly reflective metal, and light on the side surface of the groove 108. In this structure, light can be more efficiently reflected to the n-type layer 106 side. Instead of filling the gap with the p-electrode 103, a highly reflective metal film is separately provided on the side surface of the groove 108 via the insulating film 110, or a dielectric multilayer film composed of a plurality of dielectrics having different refractive indexes is formed. By doing so, the light extraction efficiency may be improved.

  As shown in FIG. 2, the n-electrode 107 has a shape having only a circular pad portion at the center of the element, and does not have a wiring-like portion for improving current diffusibility. The n-electrode 107 is made of the same material as that of the auxiliary electrode 109, that is, an n-electrode material conventionally used as an n-electrode material that contacts the + c plane (Ga-polar plane) of the n-type layer of the group III nitride semiconductor. be able to. However, with these materials, it is difficult to realize a sufficiently low contact resistance with respect to the −c plane (N polarity plane) of the n-type layer of the group III nitride semiconductor in which the n-electrode 107 is formed. A material capable of realizing a lower contact resistance with respect to the −c plane of the group nitride semiconductor may be used.

FIG. 3 is a diagram showing a planar pattern of the auxiliary electrode 109. The planar pattern of the groove 108 has substantially the same shape as the planar pattern of the auxiliary electrode 109, and only the planar pattern of the auxiliary electrode 109 will be described below. As shown in FIG. 3, the auxiliary electrode 109 has a shape and size substantially the same as the n electrode 107 at a position (element central portion) facing the n electrode 107 in a direction perpendicular to the element surface. It has a circular portion 109a. Further, the auxiliary electrode 109 has four wiring-like portions 109b extending from the circular portion 109a in the square diagonal direction. Further, the auxiliary electrode 109 has a square wiring portion 109c surrounding the outer periphery 111 of the light emitting region of the light emitting element 100, and also has a square wiring portion 109d inside the wiring portion 109c. Incidentally, the outer periphery 111 of the light emitting region is a portion indicated by a dotted line square in FIG. 2, the light emitting region is a forming region of the p-electrode 103, and substantially coincides with the region which is a forming region of the active layer 105 This is the area.

  The circular portion 109a, which is a part of the auxiliary electrode 109, is provided at a position facing the n electrode 107 in a direction perpendicular to the element surface so that a current flows more smoothly between the n electrode 107 and the auxiliary electrode 109. It is because it can be made. In addition, since the light emission at the opposed position is originally blocked by the n-electrode 107 and almost no light can be taken out, it is preferable to form a groove 108 at the opposed position so as not to emit light. One of the reasons is that it is desirable to improve this.

  The reason why the wiring-like portion 109c surrounding the outer periphery of the light emitting region is provided as a part of the auxiliary electrode 109 is as follows. When the wiring portion 109c is formed, since this wiring portion 109c is formed on the bottom surface of the groove 108, a part of the groove 108 is naturally formed in a square wiring shape surrounding the outer periphery of the light emitting region. . Conventionally, light emitted from the side surface of the element is reflected to the n-type layer 106 side by the side surface of the groove 108 surrounding the outer periphery of the light emitting region in the light emitting element 100. In general, the light emitted from the side surface of the element is not effectively utilized. Therefore, in the light emitting element 100 having the structure in which the light is reflected to the n-type layer 106 side by the wiring portion 109c, the substantial efficiency is improved. Yes.

  On the surface of the n-type layer 106 on the side where the n-electrode 107 is bonded, fine irregularities 113 are formed except for the region where the n-electrode 107 is formed. The fine irregularities 113 are formed with a large number of minute hexagonal pyramids, and the side surfaces of the hexagonal pyramids form an angle of about 60 degrees with respect to the element surface direction. This fine unevenness 113 improves the light extraction efficiency. The n electrode 107 forming region on the surface of the n-type layer 106 on the side where the n electrode 107 is bonded is not formed with fine irregularities 113 and remains flat, but this is fine with the back surface of the n electrode 107. This is to prevent the light from being reflected and attenuated between the surface of the unevenness 113 and deteriorating the light extraction efficiency.

In the light emitting element 100, a groove 108 reaching the n-type layer 106 from the p-type layer 104 side is formed, and an auxiliary electrode 109 is provided on the bottom surface of the groove 108. Here, the bottom surface of the groove 108 is the + c plane of the n-type layer 106 that is a group III nitride semiconductor, and the auxiliary electrode 109 can contact the bottom surface of the groove 108 with sufficiently low resistance. Therefore, electrons supplied from the n-electrode 107 and reach the auxiliary electrode 109 through the n-type layer 106 can flow through the auxiliary electrode 109 formed in a wiring shape and diffuse widely in the element surface direction, and emit light. Uniformity can be improved. By providing the auxiliary electrode 109, the current diffusibility in the element surface direction is improved, so that the necessity of diffusing current in the surface direction by the n electrode 107 is reduced, and the area occupied by the n electrode 107 is reduced. It can be made smaller than Actually, the n-electrode 107 of the light-emitting element 100 has only a pad portion and does not have a wiring-like portion. The area occupied by the n-electrode 107 is smaller than that of the conventional light-emitting element, and the auxiliary electrode area of the n-electrode 107 than the area of 1 09 is smaller. When the area of the n-electrode 107 is reduced, the ratio of light reflected and absorbed by the n-electrode 107 is reduced, and the light extraction efficiency is improved. As described above, the light emitting element 100 has a structure in which the light extraction efficiency is improved without impairing the uniformity of light emission.

  Further, since the side surface of the groove 108 is inclined so that the cross-sectional area in the element surface direction decreases as it goes from the p-type layer 104 to the n-type layer 106, light propagating in the element surface direction by the side surface of the groove 108 is n-type. The light can be reflected toward the layer 106, and the light extraction efficiency can be improved. Since part of the groove 108 is formed so as to surround the outside of the light emitting region, the light emitted from the side surface of the conventional element is reflected to the n-type layer 106 side by the side surface of the groove 108. Since the light emitted from the side surface of the element has not been effectively used in general, it is substantially efficient to form a part of the groove 108 so as to surround the outside of the light emitting region. Has been increased.

  Next, a manufacturing process of the light emitting element 100 will be described with reference to FIG.

First, an n-type layer 106 made of a group III nitride semiconductor, an active layer 105, and a p-type layer 104 are sequentially stacked on the sapphire substrate 115 by MOCVD (FIG. 4.A). Raw material gas used in the MOCVD method, as the nitrogen source, ammonia (NH _3), as a Ga source, trimethyl gallium _{(Ga (CH 3) 3)} , as an In source, trimethylindium _{(In (CH 3) 3)} , Al source Trimethylaluminum (Al (CH ₃ ) ₃ ), silane (SiH ₄ ) as an n-type doping gas, cyclopentadienylmagnesium (Mg (C ₅ H ₅ ) ₂ ) as a p-type doping gas, and H as a carrier gas ₂ and N ₂ . The surface of the sapphire substrate 115 may be subjected to uneven processing. In addition to the sapphire substrate 115, SiC, ZnO, spinel, or the like can be used.

Next, a mask made of SiO ₂ having a pattern in which a window is opened in a region where the groove 108 is to be formed is formed on the p-type layer 104, and dry etching using chlorine-based gas plasma is performed. Thus, almost the same groove 108 depth reaching the n-type layer 106 that is formed to the pattern of the auxiliary electrode 109. Thereafter, the mask is removed with buffered hydrofluoric acid or the like (FIG. 4.B).

  Next, the auxiliary electrode 109 is formed at a distance from the side surface of the groove 108 so as to contact the bottom surface of the groove 108 and not to contact the side surface of the groove 108 (FIG. 4.C). The alloying process of the auxiliary electrode 109 may be performed at any timing after the auxiliary electrode 109 is formed, may be performed only for the purpose of alloying the auxiliary electrode 109, or may be alloyed together with the p electrode 103 to be formed later. You may go.

  Subsequently, an insulating film 110 is continuously formed on the side surface of the groove 108, the bottom surface of the groove 108 where the auxiliary electrode 109 is not formed, the side surface of the auxiliary electrode 109, and the upper surface of the auxiliary electrode 109. The side surfaces of the auxiliary electrode 109 and the groove 108 are covered (FIG. 4.D).

  Next, the p-electrode 103 is formed on the p-type layer 104 and the insulating film 110 by sputtering, and the low melting point metal layer 102 is further formed thereon (FIG. 4.E).

  Next, the support body 101 is prepared, and the support body 101 and the p electrode 103 are joined via the low melting-point metal layer 102 (FIG. 4.F). A diffusion prevention layer (not shown) may be formed in advance between the p electrode 103 and the low melting point metal layer 102 to prevent the metal of the low melting point metal layer 102 from diffusing to the p electrode 103 side.

  Then, laser light is irradiated from the sapphire substrate 115 side, and the sapphire substrate 115 is separated and removed by laser lift-off (FIG. 4.G).

Next, a mask made of SiO ₂ is formed on the surface of the n-type layer 106 exposed by the removal of the sapphire substrate 115 and the n-electrode 107 is formed later, and TMAH (tetramethyl hydroxide) having a concentration of 22% is formed. By immersing the wafer in an (ammonium) aqueous solution, fine irregularities 113 are formed in the region of the surface of the n-type layer 106 not covered with the mask. Thereafter, the mask is removed with buffered hydrofluoric acid (FIG. 4.H). As a result, fine irregularities 113 are formed in areas other than the n-electrode 107 formation region on the surface of the n-type layer 106, and the n-electrode 107 formation region remains flat without the fine irregularities 113 being formed. In addition to TMAH, an aqueous solution such as KOH or NaOH can be used to form the fine irregularities 113.

  Next, the n-electrode 107 is formed on the flat n-type layer 106 where the fine unevenness 113 is not formed by a lift-off method using a resist. Then, the support 101 is polished and thinned, a back electrode (not shown) is formed on the surface of the support 101 opposite to the low melting point metal layer 102 side, and chip separation by laser dicing is performed to obtain FIG. The light emitting device 100 shown is manufactured.

  The n electrode and auxiliary electrode patterns are not limited to those shown in the first embodiment, and may be any patterns. However, a symmetrical pattern is desirable in order to improve the current diffusibility in the element surface direction and improve the uniformity of light emission. Further, it is desirable that a part of the auxiliary electrode and a part or all of the n-electrode are opposed to each other in a direction perpendicular to the element surface, and the opposed region is desirably as wide as possible. Further, it is desirable that a part of the auxiliary electrode has a wiring-like portion surrounding the outer periphery of the light emitting region. Examples of n electrode and auxiliary electrode patterns are listed below.

FIG. 5A shows a pattern of another n-electrode 206, and FIG. 5B shows a pattern of another auxiliary electrode 209. As shown in FIG. 5A, the n-electrode 206 has two pad portions 206a at diagonal positions of a square in a square light emitting element in plan view. The shape of the pad portion 206a is a square. Further, the n-electrode 206 has a square wiring portion 206b connected to the pad portion 206a inside the outer periphery 211 of the light emitting region. On the other hand, the auxiliary electrode 209 has two square portions 209a having the same area and shape as the pad portion 206a at a position facing the pad portion 206a in the direction perpendicular to the element surface. Further, the auxiliary electrode 209 has a lattice-like portion 209b connected to the two square portions 209a. The pattern of the n-electrode 206 and the auxiliary electrode 209 shown in FIG. 5 are both symmetric with respect to the diagonal of the square, the square portion of the pad portion 206 a and the auxiliary electrode 209 of the n-electrode 206 209a face each other, The area of the n electrode 206 is a pattern smaller than the area of the auxiliary electrode 209. Therefore, the light extraction efficiency can be improved without impairing the light emission uniformity of the light emitting element.

FIG. 6A shows a pattern of another n-electrode 306, and FIG. 6B shows a pattern of another auxiliary electrode 309. As shown in FIG. 6A, the n-electrode 306 has a circular pad portion 306a at the center of a square in a square light emitting element in plan view. The n-electrode 306 has a wiring portion 306b extending in a cross shape from the pad portion 306a. On the other hand, the auxiliary electrode 309 has a circular portion 309a having the same area and shape as the pad portion 306a at a position facing the pad portion 306a in the direction perpendicular to the element surface. Further, the auxiliary electrode 309 has a square-shaped lattice-shaped portion 309b connected to the circular portion 309a. The cross-shaped portion at the center of the lattice-shaped portion 309b faces the wiring-shaped portion 306b of the n-electrode 306 in the direction perpendicular to the element surface. Pattern of n electrodes 306 and the auxiliary electrode 309 shown in FIG. 6 are both pattern having symmetry, circle-shaped portion 309a of the pad portion 306a and the auxiliary electrode 309 of the n-electrode 306, and the n-electrode 306 The wiring portion 306b and the cross-shaped portion of the lattice portion 309b of the auxiliary electrode 309 face each other, and the area of the n electrode 306 is a pattern smaller than the area of the auxiliary electrode 309. Therefore, the light extraction efficiency can be improved without impairing the light emission uniformity of the light emitting element.

FIG. 7A shows a pattern of another n-electrode 406 and FIG. 7B shows a pattern of another auxiliary electrode 409. As shown in FIG. 7A, the n-electrode 406 has two pad portions 406a at diagonal positions of a square in a square light emitting element in plan view. The shape of the pad portion 406a is a square. The n-electrode 406 includes a square wiring portion 406b that surrounds the outer periphery 411 of the light emitting region and is connected to the pad portion 406a. On the other hand, the auxiliary electrode 409 has a rectangular portion 409a having the same area and shape as the pad portion 406a at a position facing the two pad portions 406a in a direction perpendicular to the element surface. In addition, the auxiliary electrode 409 includes a square-shaped lattice-shaped portion 409b that surrounds the outer periphery 411 of the light emitting region and is connected to the quadrangular portion 409a. The outer peripheral portion of the lattice-like portion 409b faces the wiring-like portion 406b of the n-electrode 406 in the direction perpendicular to the element surface. The patterns of the n electrode 406 and the auxiliary electrode 409 shown in FIG. 7 are both symmetrical patterns. The pad portion 406 a of the n electrode 406, the square portion 409 a of the auxiliary electrode 409, and the n electrode 4 06 grid-like portion 4 the outer peripheral portion of 09b of the wire-like portion 406b and the auxiliary electrode 4 09 face each other, the area of the n-electrode 406 has a smaller pattern than the area of the auxiliary electrode 409. Therefore, the light extraction efficiency can be improved without impairing the light emission uniformity of the light emitting element. In addition, since the wiring-like portion 406b of the n-electrode 406 is formed at a position surrounding the outer periphery 411 of the light-emitting region, the effect of blocking light is greater than when the n-electrode 406 is disposed inside the outer periphery 411 of the light-emitting region. And the light extraction efficiency is improved.

FIG. 8A shows a pattern of another n-electrode 506, and FIG. 8B shows a pattern of another auxiliary electrode 509. As shown in FIG. 8A, the n-electrode 506 includes two pad portions 506a at diagonal positions of a square in a square light emitting element in plan view. The shape of the pad portion 506a is a square. The n-electrode 506 has a square wiring portion 506b connected to the pad portion 506a inside the outer periphery 511 of the light emitting region. On the other hand, the auxiliary electrode 509 has a grid pattern and has a square wiring portion 509a surrounding the outer periphery 511 of the light emitting region. A part of the two pad parts 506a of the n-electrode 506 and a part of the wiring-like part 509a of the auxiliary electrode 509 face each other in a direction perpendicular to the element surface. The patterns of the n electrode 506 and the auxiliary electrode 509 shown in FIG. 8 are both symmetrical patterns, and the area of the n electrode 5 06 is smaller than the area of the auxiliary electrode 5 09. Therefore, the light extraction efficiency can be improved without impairing the light emission uniformity of the light emitting element.

  In the embodiment, a region of the n-type layer facing the n-electrode and the auxiliary electrode may be etched from the n-type layer surface side to form a groove, and the n-electrode may be formed on the bottom surface of the groove. . Since the thickness of the n-type layer in the region where the n electrode and the auxiliary electrode face each other is reduced and the conduction between the n electrode and the auxiliary electrode becomes easier, the area of the n electrode is reduced and the light extraction efficiency is improved. Further improvement is possible.

  In the embodiment, laser lift-off is used to remove the sapphire substrate, but a buffer layer that can be dissolved in a chemical solution is formed between the sapphire substrate and the n-type layer, and the chemical solution is used after bonding to the support. Chemical lift-off in which the buffer layer is dissolved to separate and remove the sapphire substrate may be used.

  The group III nitride semiconductor light-emitting device of the present invention can be used for lighting devices, display devices, and the like.

DESCRIPTION OF SYMBOLS 101: Support body 102: Low melting-point metal layer 103: P electrode 104: P type layer 105: Active layer 106: N type layer 107: N electrode 108: Groove 109: Auxiliary electrode 110: Insulating film 111: Outer periphery of light emitting region 113 : Fine irregularities

Claims (5)

A conductive support, a p-electrode positioned on the support, a p-type layer made of a group III nitride semiconductor, an active layer, an n-type layer, and the n-type layer, which are sequentially positioned on the p-electrode A group III nitride semiconductor light-emitting device having an n-electrode positioned above,
A groove formed in a wiring-like pattern at a depth reaching the n-type layer from the p-electrode-side surface of the p-type layer;
An auxiliary electrode formed in a wiring pattern that is in contact with the n-type layer that is the bottom surface of the groove and not in contact with the side surface of the groove;
A transparent insulating film covering the auxiliary electrode and the bottom and side surfaces of the groove;
I have a,
A group III nitride semiconductor light emitting device, wherein the area of the n electrode is smaller than the area of the auxiliary electrode . 2. The group III nitride semiconductor light-emitting device according to claim 1 , wherein a side surface of the groove has an inclination in which a cross-sectional area in the element surface direction of the groove decreases toward the n-type layer side. 3. The group III nitride semiconductor light-emitting element according to claim 1, wherein at least a part of the auxiliary electrode is formed at a position facing a part or all of the n electrode. It said groove and said portion of the auxiliary electrode, III-nitride semiconductor light emitting device according to any one of claims 1 to claim 3, characterized in that it has an outer peripheral shape of wiring portion surrounding the outside of the light-emitting region . The group III nitride according to any one of claims 1 to 4 , wherein the auxiliary electrode is made of V / Al, Ti / Al, V / Au, Ti / Au, or Ni / Au. Semiconductor light emitting device.

Images