JP2011198997A - Group iii nitride semiconductor light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a light extraction efficiency of a group III nitride semiconductor light emitting element.SOLUTION: The light emitting element 100 includes a first groove 108 formed on a surface on a side of a p-type layer 104 bonded to a p-type electrode 103. The groove 108 has a depth enough to penetrate the p-type layer 104 and an active layer 105 and reach an n-type layer 106. An auxiliary electrode 109 is formed in contact with a bottom face of the groove 108 but not in contact with a side face of the groove 108. Moreover, an insulating film 110 consisting of SiOis formed continuously on the side face of the groove 108, the bottom face of the groove where the auxiliary electrode 109 is not formed, and the auxiliary electrode 109. A second groove 111 so deep as to reach the auxiliary electrode 109 is formed on a surface opposite from the active layer 105 side of the n-type layer 106 in a region facing a part of the auxiliary electrode 109. An n-electrode 107 consisting of a pad part alone is formed on the auxiliary electrode 109 exposed on a bottom face of the second groove 111.

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.

  According to a first aspect of the present invention, there is provided 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 the group III nitride semiconductor light-emitting device having the n-electrode, the first groove having a depth reaching the n-type layer from the p-electrode-side surface of the p-type layer, and the n-type layer exposed by the first groove An auxiliary electrode that is in contact with the first groove and is not in contact with the side surface of the first groove; an auxiliary electrode; a light-transmitting insulating film that covers the bottom and side surfaces of the first groove; And a second groove having a depth reaching the auxiliary electrode from the surface opposite to the p-electrode side of the n-type layer, the n-electrode having only a pad portion. A group III nitride semiconductor light-emitting device comprising: and located on and in contact with the auxiliary electrode exposed by the second groove

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 13 elements (group 3B elements) B or Tl, and part of N is replaced with other group 15 elements (group 5B 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 have any shape as long as it is composed only of the pad portion, and is, for example, circular or square. The number of pad portions may be arbitrary, but from the viewpoint of current diffusivity, it is desirable to have an arrangement with symmetry with respect to the element shape. For example, it is preferable to arrange one pad portion at the center of the element, or to arrange two pad portions at diagonal positions of the rectangle when the element shape is rectangular. Further, it is desirable that the n electrode is in contact with the auxiliary electrode in as large an area as possible, and the shape of the n electrode is preferably included in the shape of the auxiliary electrode in plan view. This is because conduction between the auxiliary electrode and the n electrode is facilitated.

  The first groove and the auxiliary electrode may have an arbitrary pattern, but a wiring-like pattern having symmetry 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 first groove and the pattern of the auxiliary electrode may not match, and the pattern of the auxiliary electrode may be a part of the pattern of the first groove. It is desirable to provide a part of the auxiliary electrode with the same area and shape as the pad part at a position facing the pad part of the n electrode in the direction perpendicular to the element surface. In addition, a part of the first 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. When the first groove and part of the auxiliary electrode have such a pattern, light conventionally emitted from the side surface of the element can be reflected to the n-type layer side by the side surface of the first groove. However, since light emitted from the side surface of the element is generally not effectively used, substantial increase in efficiency can be achieved. The first groove may also serve as an element isolation groove formed on the outer periphery of the element region.

  The side surface of the first groove is desirably inclined so that the cross-sectional area of the first groove in the element surface direction decreases toward the n-type layer side. This is because the light propagating in the element surface direction can be reflected to the n-type layer side by the side surface of the first groove, and the light extraction efficiency can be further improved. The angle formed by the side surface of the first 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. As the material for the n-electrode, any material can be used because the n-electrode is directly joined to the auxiliary electrode. The same material as the auxiliary electrode may be used. In particular, it is desirable that the n electrode has a structure of two or more layers, and a layer in contact with the auxiliary electrode among the two or more layers is made of a material having nitrogen reactivity. Strong adhesion to the auxiliary electrode can be obtained. Examples of the material having nitrogen reactivity include Ti, V, Zr, W, Ta, and Cr.

  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.

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 invention is a group III nitride semiconductor light emitting device according to the first invention, wherein the first groove and the auxiliary electrode are wiring patterns.

  According to a third invention, in the first invention or the second invention, the side surface of the first groove has an inclination in which the cross-sectional area in the element surface direction of the groove decreases toward the n-type layer side. And a group III nitride 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 auxiliary electrode has a shape including the shape of the n electrode in plan view.

  According to a fifth invention, in the first to fourth inventions, the group III nitride semiconductor light-emitting element is rectangular, and the n-electrode is two pad portions respectively positioned at diagonal positions of the rectangle. A group III nitride semiconductor light-emitting device characterized by the following.

  A sixth invention is a group III nitride semiconductor light-emitting device according to the first to fourth inventions, wherein the n-electrode is one pad portion located in a central region of the device.

  A seventh invention is a group III nitride according to the first to sixth inventions, wherein the first groove and a part of the auxiliary electrode are wiring patterns surrounding the outside of the light emitting region It is a semiconductor light emitting device.

  An eighth invention is the group III according to the first to seventh inventions, wherein 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, and the n electrode is continuous with the auxiliary electrode. Since this auxiliary electrode is in contact with the + c plane of the n-type layer of the group III nitride semiconductor exposed at the bottom 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. In addition, since the n electrode is only the pad portion and is not located on the light emitting region, the light extraction is not hindered by the presence of the n electrode, and the light extraction efficiency can be improved. Moreover, since the voltage drop based on the sheet resistance of the n-type layer is greatly reduced, the drive voltage can be lowered.

  Further, according to the second invention, the current diffusibility in the element surface direction by the auxiliary electrode is further improved, and the uniformity of light emission can be further improved.

  According to the third invention, the light confined in the surface of the element by the side surface of the first groove can be reflected upward, and the light extraction efficiency can be improved.

  According to the fourth invention, since the n electrode contacts the auxiliary electrode in a wide area, the conduction between the auxiliary electrode and the n electrode is facilitated, and as a result, the area of the n electrode can be reduced. The optical output can be improved by enlarging.

  In addition, according to the fifth and sixth inventions, since the pad portion of the n-electrode is arranged as a target, the current diffusibility in the element surface direction is further improved, and the uniformity of light emission can be further improved.

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

  Further, as in the eighth invention, V / Al, Ti / Al, V / Au can be used as the material of the auxiliary electrode.

FIG. 3 is a plan view of the light emitting device 100 according to the first embodiment as viewed from above. FIG. 2 is a cross-sectional view of the light-emitting element 100 taken along line AA in FIG. The figure which showed the pattern of the auxiliary electrode 109. FIG. 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. FIG. 10 shows a manufacturing process of the light-emitting element 100. The figure which showed the pattern of the n electrode 207. FIG. The figure which showed the pattern of the auxiliary electrode 209. FIG.

  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 plan view of the light emitting device 100 of Example 1 as viewed from above, and FIG. 2 is a cross-sectional view taken along line AA in FIG. As shown in FIG. 1, the light emitting element 100 is square in plan view. As shown in FIG. 2, the light emitting device 100 includes a support 101, a p-electrode 103 bonded to the support 101 via a low-melting point metal layer 102, and a III layer sequentially stacked on the p-electrode 103. A p-type layer 104 made of a group nitride semiconductor, an active layer 105, an n-type layer 106, an n-pad electrode 107, and an auxiliary electrode 109 are included.

  As the support 101, a conductive substrate made of Si, GaAs, Cu, Cu—W, or the like can be used. A back electrode 113 is formed on the back surface of the support 101 (the surface opposite to the p electrode 103 side), and the light emitting element 100 is configured to conduct in a direction perpendicular to the element surface. 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 first groove 108 is formed on the surface of the p-type layer 104 on the side bonded to the p-electrode 103. The first 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 first groove 108 is inclined so that the cross-sectional area in the element surface direction decreases from the p-type layer 104 toward the n-type layer 106, and the bottom surface of the first groove 108 is parallel to the element surface. .

  The inclination angle of the side surface of the first 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 first groove 108, and the auxiliary electrode 109 is in contact with the bottom surface of the first groove 108 where the n-type layer 106 is exposed, and on the side surface of the first groove 108. It is formed not to touch. In addition, an insulating film 110 made of SiO ₂ is formed on the side surface of the first 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 metal film (for example, Al or Cr) having high reflectivity and good adhesion to the insulating film 110 is separately provided on the side surface of the groove 108 via the insulating film 110, or refracted. The light extraction efficiency may be improved by forming a dielectric multilayer film composed of a plurality of dielectrics having different rates. The insulating film 110 itself may be a dielectric multilayer film.

  As shown in FIG. 1, the second groove 111 is a surface of the n-type layer 106 on the side opposite to the active layer 105 side, and has two outer peripheral portions of the square light emitting element 100 and two diagonal positions. It is formed at the corner. The second groove 111 has a depth at which the auxiliary electrode 109 is exposed, and the auxiliary electrode 109 is exposed on the bottom surface of the second groove 111 at two corners at diagonal positions.

  The n-electrode 107 is composed of two square pad portions. As shown in FIG. 1, the n-electrode 107 has two corner portions at the diagonal positions of the square light emitting device 100, and is formed at the two corner portions. It is formed on the bottom surface of the second groove 111. The auxiliary electrode 109 and the n-electrode 107 exposed on the bottom surface of the second groove 111 are directly connected. Therefore, any material can be used for the n-electrode 107. The same material as the auxiliary electrode 109 may be used. In particular, it is desirable that the n-electrode 107 has two or more layers, and a layer in contact with the auxiliary electrode 109 among the two or more layers is made of a material having nitrogen reactivity. Strong adhesion to the auxiliary electrode 109 is obtained. Examples of the material having nitrogen reactivity include Ti, V, Zr, W, Ta, and Cr.

  FIG. 3 is a diagram showing a planar pattern of the auxiliary electrode 109. The planar pattern of the groove 108 is substantially the same shape as the planar pattern of the auxiliary electrode 109. As shown in FIGS. 1 and 3, the auxiliary electrode 109 is located at a position facing the n-electrode 107 in the direction perpendicular to the element surface (two corners at diagonal positions of the square light-emitting element 100). , And has a square portion 109a of a size that encloses the n-electrode 107 in plan view. Further, the auxiliary electrode 109 has a grid-like portion 109b constituted by wiring parallel to the sides of the square light emitting element 100, following the square portion 109a. Further, the auxiliary electrode 109 has a square wiring portion 109 c that surrounds the outer periphery 112 of the light emitting region of the light emitting element 100. The outer periphery 112 of the light emitting region is a portion indicated by a two-dot chain line in FIG. 1, and the light emitting region is a region where the p electrode 107 is formed and substantially coincides with a region where the active layer 105 is formed. It is an area.

  As described above, by providing the square portion 109 a as a part of the auxiliary electrode 109, a current flows smoothly from the auxiliary electrode 109 to the n electrode 107. 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 forming the wiring portion 109c, since the wiring portion 109c is formed on the bottom surface of the first groove 108, a part of the first groove 108 naturally has a square surrounding the outer periphery 112 of the light emitting region. It is formed in a wiring shape. 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 first 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.

  It is desirable that fine irregularities be formed on the surface of the n-type layer 106 opposite to the active layer 105 side. This fine unevenness can improve the light extraction efficiency. Fine irregularities can be formed by wet etching, and a large number of minute hexagonal pyramids whose side surfaces form an angle of about 60 degrees with respect to the element surface direction can be formed.

  In the light emitting element 100, a first 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 first 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. A part of the auxiliary electrode 109 is in direct contact with the n-electrode 107. Therefore, electrons supplied from the n-electrode 107 and reach the auxiliary electrode 109 can flow through the auxiliary electrode 109 formed in a wiring shape and can be diffused widely in the element surface direction, so that the uniformity of light emission can be improved. . Moreover, since the voltage drop based on the sheet resistance of the n-type layer 106 is reduced, the drive voltage can be lowered. Further, since the n-electrode 107 is only a pad portion and is provided on the auxiliary electrode 109, the n-electrode 107 is not located on the light emitting region at all. Therefore, the n-electrode 107 does not hinder light extraction, and the light extraction efficiency is improved as compared with the conventional light emitting element. Further, the light component propagating in the element surface direction in the peripheral region of the active layer 105 and confined in the element surface is reflected at the interface between the insulating film 110 and the p-electrode 103 along the inclined side surface of the first groove 108. As a result, the direction changes to the n-type layer 106 side. Therefore, the light component emitted from the surface opposite to the active layer 105 side of the n-type layer 106 increases, and the light extraction efficiency is improved.

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

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 is formed on the p-type layer 104 in a region where the first groove 108 is to be formed, and dry etching using chlorine-based gas plasma is performed. As a result, a first groove 108 having a depth reaching the n-type layer 106 substantially matching the pattern shape of the auxiliary electrode 108 is formed. 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 first groove 108 so as to contact the bottom surface of the first groove 108 and not to contact the side surface of the first 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, the insulating film 110 is formed in a film shape continuously on the side surface of the first groove 108, the bottom surface of the first 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. Then, the auxiliary electrode 109 and the side surfaces of the trench 108 are covered with the insulating film 110 (FIG. 4.D). As described above, the formation of the first groove 108 exposes a junction on the side surface of the first groove 108, but it can be immediately protected by the insulating film 110, and current leakage can be reliably prevented. is there.

  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, the sapphire substrate 115 is separated and removed by laser lift-off (FIG. 4.G), and the surface of the n-type layer 106 exposed by removing the sapphire substrate 115 is washed with hydrochloric acid. . Since the surface exposed by the removal of the sapphire substrate 115 is the N-polar surface of the n-type layer 106, it is not necessary to form the insulating film 110 for protecting the junction after the laser lift-off. A protective film may be formed afterwards for the purpose of protection from damage.

Next, on the surface of the n-type layer 106 exposed by the removal of the sapphire substrate 115, a mask made of SiO ₂ having a pattern in which a window is opened in a region where the second groove 111 is to be formed is used, and chlorine-based gas plasma is used. Perform dry etching. As a result, a second groove 111 having a depth reaching the auxiliary electrode 109 is formed. At this time, by providing a Pt layer in the auxiliary electrode 109, the Pt layer can function as an etching stopper. Thereafter, the mask is removed with buffered hydrofluoric acid or the like (FIG. 4.H).

  Next, an n-electrode 109, which is a square pad portion, is formed on the square portion 109a of the auxiliary electrode 109 exposed by the formation of the second groove 111 by a lift-off method (FIG. 4.I). Then, the support 101 is polished and thinned, a back electrode 113 is formed on the surface of the support 101 opposite to the low melting point metal layer 102 side, and an element isolation portion (a portion indicated by a dotted line in FIG. 4.I). ) To separate the elements, and individual light emitting elements 100 are manufactured.

  The auxiliary electrode pattern is not limited to that shown in the first embodiment, and may be any pattern. Also, the number of n-electrode pad portions and the arrangement pattern are arbitrary. However, in order to improve the current diffusibility in the element surface direction and improve the uniformity of light emission, it is desirable that the auxiliary electrode and the n electrode have a symmetrical pattern. Further, it is desirable that the n electrode pattern is included in the auxiliary electrode pattern in plan view so that the n electrode is in wide contact with the auxiliary electrode. 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. Other patterns of the n electrode and the auxiliary electrode are shown below.

  FIG. 5 is a diagram showing another n-electrode 207 pattern, and FIG. 6 is a diagram showing another auxiliary electrode 209 pattern. As shown in FIG. 5, the n-electrode 207 has one circular pad portion at the center of a square in a square light emitting element in plan view. On the other hand, as shown in FIG. 6, the auxiliary electrode 209 has a slightly larger circular portion 209 a that encloses the n electrode 207 in a plan view at a position facing the n electrode 207 in the direction perpendicular to the element surface. Yes. Further, the auxiliary electrode 209 has four wiring-like portions 209b extending from the circular portion 209a in a square diagonal direction. Further, the auxiliary electrode 209 has a square wiring portion 209c surrounding the outer periphery 212 of the light emitting region of the light emitting element, and similarly has a square wiring portion 209d inside the wiring portion 209c. Such a pattern of the n-electrode 207 and the auxiliary electrode 209 can also improve the light emission uniformity of the light-emitting element and improve the light extraction efficiency as in the first embodiment.

  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: 1st groove | channel 109: Auxiliary electrode 110: Insulating film 111: 2nd Groove

Claims (8)

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 an n-electrode, which are sequentially positioned on the p-electrode, In a group III nitride semiconductor light emitting device having:
A first groove having a depth reaching the n-type layer from the p-electrode side surface of the p-type layer;
An auxiliary electrode in contact with the n-type layer exposed by the first groove and not in contact with a side surface of the first groove;
A transparent insulating film covering the auxiliary electrode and the bottom and side surfaces of the first groove;
A second groove located in a region facing a part of the auxiliary electrode in a direction perpendicular to the element surface and having a depth reaching the auxiliary electrode from the surface of the n-type layer opposite to the p electrode side When,
Have
The n electrode is composed of only a pad portion, and is positioned in contact with the auxiliary electrode exposed by the second groove.
A group III nitride semiconductor light emitting device characterized by the above.   2. The group III nitride semiconductor light emitting device according to claim 1, wherein the first groove and the auxiliary electrode have a wiring pattern. 3.   3. The group III according to claim 1, wherein a side surface of the first 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. Nitride semiconductor light emitting device.   4. The group III nitride semiconductor light-emitting device according to claim 1, wherein the auxiliary electrode has a shape including an n-electrode shape in plan view. 5. The group III nitride semiconductor light emitting device is rectangular,
5. The group III nitride semiconductor light-emitting device according to claim 1, wherein the n-electrode is two pad portions respectively positioned at diagonal positions of the rectangle.   5. The group III nitride semiconductor light-emitting device according to claim 1, wherein the n-electrode is one pad portion located in a central region of the device.   7. The group III nitride according to claim 1, wherein a part of the first groove and the auxiliary electrode is a wiring pattern surrounding an outside of a light emitting region. 8. Semiconductor light emitting device.   The group III nitride according to any one of claims 1 to 7, wherein the auxiliary electrode is made of V / Al, Ti / Al, V / Au, Ti / Au, or Ni / Au. Semiconductor light emitting device.

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