Light emitting diode device

The present invention relates to a light emitting diode element (hereinafter, also referred to as LED element), and in particular, a translucent plate-like body including a semiconductor layer having a light emitting element structure and a metal formed on the surface of the plate-like body. The present invention relates to a light emitting diode element having a reflective film and configured such that at least a part of light generated inside the semiconductor layer is reflected by the metal reflective film and emitted to the outside of the plate-like body.

FIG. 7 is a cross-sectional view of the LED element disclosed in Patent Document 1. The conventional LED element 100 shown in FIG. 7 includes a translucent substrate 110A made of sapphire, a translucent semiconductor layer 110B made of a group 3 nitride compound semiconductor (hereinafter, also referred to as nitride semiconductor), and ITO. The translucent electrode layer 110C made of (indium tin oxide) has a translucent plate-like body 110 laminated in this order. The back surface of the translucent substrate 110A (the surface on which the translucent semiconductor layer 110B is not formed), which is one surface of the plate-shaped body 110, is made uneven by etching or mechanical processing, and is made of metal. It is covered with a reflective film 120. A buffer layer (not shown) is interposed between the translucent substrate 110A and the translucent semiconductor layer 110B. The translucent semiconductor layer 110B has an n-type layer 110B-1 and a p-type layer 110B-2 constituting a pn junction type light emitting device structure, and an active layer is preferably provided at the pn junction. .. A negative electrode 130 is formed on the surface of the n-type layer 110B-1 partially exposed by etching. A positive electrode 140 is formed on a part of the upper surface of the translucent electrode layer 110C.

Here, the nitride semiconductor is a general formula Al._aIn_bGa_1-abA compound semiconductor represented by N (0 a 1, 0 b 1, 0 a + b 1), which has an arbitrary composition such as GaN, InGaN, AlGaN, AlInGaN, AlN, and InN. Including. In the above chemical formula, a part of Group 3 elements is replaced with B (boron), Tl (talium), etc., and a part of N (nitrogen) is P (phosphorus), As (arsenic), Sb (antimony). , Bi (bismuth) and the like are also included in the nitride semiconductor.

In the LED element 100 shown in FIG. 7, since the reflective surface of the metal reflective film 120 is an uneven surface, the light generated inside the translucent semiconductor layer 110B and transmitted through the translucent substrate 110A is reflected by the metal. It is reflected by the film 120 in various directions. Therefore, the LED element 100 is expensive because the multiple reflection inside the plate-shaped body 110 is suppressed and the light reflected by the metal reflective film 120 is also emitted to the outside of the element from the side surface of the translucent substrate 110A. Indicates the light emission output.<patcit num="1"><text>Japanese Unexamined Patent Publication No. 10-270754</text></patcit><nplcit num="1"><text>Japanese Journal of Applied Physics, Vol. 45, No. 39, 2006, pp. L1045-L1047 (Japanese Journal of Applied Physics, Vol.45, No.39, 2006, pp.L1045-L1047)</text></nplcit>

<p>When the LED element 100 shown in FIG. 7 is fixed to a mounting member (lead frame, stem, printed circuit board, etc.) to manufacture an LED lamp, the outer surface of the metal reflective film 120 and the surface of the mounting member Adhere. At this time, since the outer surface of the metal reflective film 120 is not flat, a space is created between the LED element 100 and the mounting destination member. When such a space is created, there arises a problem that heat dissipation generated by the LED element 100 is hindered. Further, when this space is formed as bubbles, the pressure inside the bubbles fluctuates with the temperature change, so that the adhesive is stressed. This stress accelerates the deterioration of the adhesive, which causes a problem that the reliability and life of the LED lamp are lowered.</p><p>The present invention has been made in view of such circumstances, and a main object thereof is to have a metal reflective film whose reflective surface is an uneven surface, but to use the outer surface of the metal reflective film as the surface of a mounting member. It is an object of the present invention to provide a light emitting diode element in which a space is unlikely to be generated between the element and the mounting destination member when the element is fixed to the mounting destination member by adhering to the mounting destination member.</p>

<p>In order to achieve the above object, a light emitting diode element having the following features is provided. (1) It has a translucent plate-like body including a semiconductor layer having a light emitting element structure and a metal reflective film formed on the surface of the plate-like body, and at least the light generated inside the semiconductor layer. A light emitting diode element configured to be partially reflected by the metal reflective film and emitted to the outside of the plate-like body, and the surface of the plate-shaped body covered with the metal reflective film is uneven. A light emitting diode element that is a surface and the outer surface of the metal reflective film is flattened to be a mirror surface. (2) The light emitting diode element according to (1) above, wherein the plate-like body includes a translucent substrate, and the surface of the translucent substrate constitutes at least a part of the uneven surface. (3) The plate-like body contains a translucent electrode layer made of a transparent conductive film material, and the surface of the translucent electrode layer constitutes at least a part of the uneven surface. The light emitting diode element according to. (4) The light emitting diode element according to (1) above, wherein the surface of the semiconductor layer constitutes at least a part of the uneven surface. (5) The light emitting diode element according to any one of (1) to (4) above, wherein the semiconductor layer is a group 3 nitride compound semiconductor. (6) It has a translucent plate-like body including a semiconductor layer having a light emitting element structure and a metal reflective film formed on the surface of the plate-like body, and at least the light generated inside the semiconductor layer. A method for manufacturing a light emitting diode element, which is configured to be partially reflected by the metal reflective film and emitted to the outside of the plate-like body, which is a step of preparing the plate-like body and the metal. A step of processing the surface of the plate-like body to be covered with a reflective film to form an uneven surface, a step of forming a metal film constituting the metal reflective film so as to cover the uneven surface, and an outer surface of the metal film. A manufacturing method comprising a step of flattening by polishing to make a mirror surface.</p>

<p>According to the present invention, although the reflective surface has a metal reflective film having an uneven surface, the element is fixed to the mounting destination member by adhering the outer surface of the metal reflective film to the surface of the mounting destination member. At that time, it is possible to obtain a light emitting diode element in which a space is unlikely to be generated between the element and the mounting destination member.</p>

(Embodiment 1) FIG. 1 is a cross-sectional view showing the structure of the LED element according to the first embodiment. The LED element 10 is a translucent substrate 11A made of sapphire, a translucent semiconductor layer 11B made of a nitride semiconductor, and a translucent electrode layer 11C made of ITO, which are laminated in this order. It has a sex plate-like body 11. The back surface of the translucent substrate 11A, which is one of the main surfaces of the plate-shaped body 11, is an uneven surface and is covered with a metal reflective film 12. A buffer layer (not shown) is interposed between the translucent substrate 11A and the translucent semiconductor layer 11B. The translucent semiconductor layer 11B has an n-type layer 11B-1 and a p-type layer 11B-2 constituting a pn junction type light emitting device structure, and an active layer is preferably provided at the pn junction. .. A negative electrode 13 is formed on the surface of the n-type layer 11B-1 partially exposed by etching. A positive electrode 14 is formed on a part of the upper surface of the translucent electrode layer 11C.

In the LED element 10 shown in FIG. 1, since the reflective surface of the metal reflective film 12 is an uneven surface, the light generated inside the translucent semiconductor layer 11B and transmitted through the translucent substrate 11A is the metal. It is reflected in various directions by the reflective film 12. Therefore, in addition to suppressing multiple reflections inside the plate-like body 11, the light reflected by the metal reflective film 12 is also emitted to the outside of the element from the side surface of the translucent substrate 11A, so that the light emission output of the element is increased. It gets higher.

Further, in the LED element 10 shown in FIG. 1, the outer surface of the metal reflective film 12 is flattened to be a mirror surface. Therefore, when the LED element 10 is fixed to the mounting destination member to manufacture the LED lamp, no space is created between the element 10 and the mounting destination member. Therefore, the heat generated by the LED element 10 is efficiently dissipated through the mounting destination member. In addition, since air bubbles do not enter the adhesive used for adhesion, deterioration of the adhesive due to pressure changes in the air bubbles does not occur, and the reliability of the LED lamp is lowered due to the deterioration of the adhesive. The problem of shortening the life does not occur.

The LED element 10 shown in FIG. 1 can be manufactured as follows. First, known vapor phase epitaxial growth methods such as organic metal compound vapor deposition (MOVPE) method, hydride vapor phase growth (HVPE) method, and molecular beam epitaxy (MBE) method are used on a translucent substrate 11A made of sapphire. A buffer layer made of a nitride semiconductor (not shown), an n-type layer 11B-1 made of a nitride semiconductor, and a p-type layer 11B-2 made of a nitride semiconductor are sequentially grown and laminated to be translucent. The semiconductor layer 11B is formed. The buffer layer is, for example, a low temperature buffer layer made of GaN, AlGaN, AlN, or the like. Preferably, a single crystal high temperature buffer layer made of undoped GaN is laminated on the low temperature buffer layer. The n-type layer 11B-1 is, for example, a Si-doped GaN layer. The p-type layer 11B-2 has, for example, a two-layer structure by laminating an Mg-doped AlGaN clad layer and an Mg-doped GaN contact layer. At the junction between the n-type layer 11B-1 and the p-type layer 11B-2, for example, an active layer having a multiple quantum well structure including an InGaN well layer is provided. Annealing treatment and electron beam irradiation treatment for activating the p-type impurities added to the p-type layer 11B-2 can be appropriately performed.

After the translucent semiconductor layer 11 is formed, the translucent electrode layer 11C made of ITO is next formed on the surface of the p-type layer 11B-2. The forming method includes CVD method (thermal CVD, plasma CVD, MOCVD, optical CVD), spray method, sputtering method, vacuum deposition method, cluster beam deposition method, pulse laser deposition method, ion plating method, solgel method, laser. An ablation method or any other known method for forming an ITO thin film can be used arbitrarily. Au, Ni / formed between the p-type layer 11B-2 and the translucent electrode layer 11C made of ITO to have a film thickness of several Å to several tens of Å as a layer for reducing contact resistance. A translucent metal thin film made of Au or the like may be interposed. The translucent electrode layer 11C shall be formed using a transparent conductive film material other than ITO, such as indium oxide, tin oxide, zinc oxide, IZO (indium zinc oxide), FTO (fluorine-doped tin oxide), and titanium nitride. You can also. After the translucent electrode layer 11C is formed, the positive electrode 14 is formed on a part of the upper surface thereof using Ti, Au, Al, Cu, or the like. The positive electrode 14 is a bonding pad for wire bonding.

In the LED element 10, instead of the translucent electrode layer 11C, a thin film metal electrode having translucency or an open metal electrode provided with an opening through which light generated inside the translucent semiconductor layer 11B can pass. Can also be formed. These electrodes are formed with a simple substance or alloy such as Au, Ni, Co, Platinum Group Metals, etc., at least in contact with the p-type layer so as to form ohmic contact with the p-type layer 11B-2. To do.

After forming the positive electrode 14, the n-type layer 11B is then etched from the surface side of the p-type layer 11B-2 to a depth reaching the n-type layer 11B-1 by using a reactive ion etching method. Partially expose the surface of -1. Then, the negative electrode 13 is formed on the surface of the exposed n-type layer 11B-1. The negative electrode 13 is formed of at least a portion in contact with the n-type layer with a simple substance such as Al, Ti, W, Ni, Cr, V, or an alloy so as to form ohmic contact with the n-type layer 11B-1. When a conductive substrate (semiconductor substrate) such as a SiC substrate, a GaN substrate, or a ZnO substrate is used as the translucent substrate instead of an insulating substrate such as a sapphire substrate, the negative electrode is used as the surface of the n-type layer. It is also possible to form it on the back surface of the translucent substrate without forming it. After forming the negative electrode 13, it is preferable to form an insulating protective film on the surface of the element excluding the surface of the electrode.

After the negative electrode 13 is formed, the back surface of the translucent substrate 11A is processed into an uneven surface. As one method, fine particles made of polymer, metal, etc. having a particle size of micron order or submicron order are deposited on the back surface of the translucent substrate, and this is used as a mask (random etching mask) to form a translucent substrate. The back surface is etched to form recesses. In another method, a photoresist film is formed on the back surface of the translucent substrate, and an aperture pattern is formed on the photoresist film by using a photolithography technique, which can be used as an etching mask. This method has the advantage that the machining area can be controlled. For example, on the back surface of the translucent substrate 11A, the area through which the dividing line passes when the wafer is divided into chips in a later process is left flat, and the other areas are processed to make an uneven surface. By not forming the metal reflective film 12 in the region through which the dividing line passes, the degree of freedom in selecting the method for dividing the wafer can be increased. The etching method for forming the recesses on the back surface of the translucent substrate is not limited, and any of a dry etching method such as plasma etching and reactive ion etching and a wet etching method using an etching solution can be adopted.

In order to process the back surface of the translucent substrate 11A into an uneven surface, a mechanical processing method can be used as a method other than etching. For example, the back surface of the translucent substrate can be made an uneven surface by grinding or polishing with relatively coarse polishing particles. Alternatively, the back surface of the translucent substrate can be made an uneven surface by cutting using a dicing blade or the like.

In order to make the back surface of the translucent substrate 11A an uneven surface, not only the above-mentioned subtractive processing method but also an additive processing method can be used. That is, it is a method of adding a protruding portion to be a convex portion on the uneven surface on the back surface of the translucent substrate. The material of such a protruding portion may be any one having translucency, and is not particularly limited, but is preferably formed of a translucent material having a small difference in refractive index from the translucent substrate. For example, when the translucent substrate is a sapphire substrate, preferred materials for the protrusions include aluminum oxide, spinel, ITO and the like. As a method for forming the protruding portion, a vapor phase deposition method such as vapor deposition, sputtering, or CVD is preferably exemplified. When the vapor phase volume method capable of low-temperature film formation is used, the protrusion can be formed in a desired pattern by the lift-off method using a photolithography technique.

When the back surface of the translucent substrate 11A is a concavo-convex surface, the structure of the concavo-convex surface is not particularly limited, and a structure consisting of a continuous convex portion and an isolated concave portion (for example, a hemispherical or circular shape in places on a flat surface). A structure consisting of a columnar, prismatic, conical, truncated cone, prismatic, truncated cone, etc. with open holes, a structure consisting of continuous concave portions and isolated convex portions (for example, in places on a flat surface). Hemispherical, cylindrical, prismatic, conical, truncated cone-shaped, prismatic, prismatic-shaped, etc.), ridge-shaped protrusions and groove-shaped recesses alternate Structures lined up in (the shape of the cross section of the convex part and the concave part includes a triangular shape, a trapezoidal shape, a square shape, etc., and the convex part and the concave part extend linearly or curvedly. Examples thereof include those having a convex portion or a concave portion having a branch, etc.), and various structures such as a structure in which these are mixed can be used. The shapes (upper surface shape, cross-sectional shape) and arrangement of the convex portions and the concave portions on the uneven surface may be regular or irregular. Preferably, when the side wall surface of the convex portion or the concave portion is an inclined surface having an inclination angle of 30 to 60 degrees, the light is reflected by the reflective surface of the metal reflective film formed on the uneven surface. Since the degree of change in the light propagation direction is large, the effect of improving the output of the LED element is large.

The minimum value of the depth of the concave portion when the concave portion is formed by etching on the back surface of the translucent substrate 11A and the height of the convex portion when the convex portion is formed by the vapor phase volume method is preferably 0.5 μm. The above setting is more preferably set to 1 μm or more, and particularly preferably 5 μm or more. When the uneven surface is formed by mechanical processing, the surface roughness (arithmetic mean roughness Ra) of the uneven surface is preferably 0.1 μm or more, and more preferably 0.2 μm or more. There is no particular upper limit to the height difference between the concave and convex parts on the uneven surface, but considering the time and energy required to process the substrate and the time and energy required to embed the concave and convex parts on the uneven surface with the metal reflective film in the next step. The maximum value of the height difference is preferably 50 μm or less, and more preferably 25 μm or less.

After the back surface of the translucent substrate 11A is processed into an uneven surface, a metal reflective film 12 covering the uneven surface is formed. To form the metal reflective film 12, first, the metal film constituting the metal reflective film 12 is formed so as to cover the uneven surface and fill the concave portion of the uneven surface. Examples of the method for forming the metal film in this way include vapor deposition methods such as CVD, sputtering, and thin film deposition, and electrolytic plating which is a wet method. When the concave portion of the uneven surface is hole-shaped or groove-shaped and the ratio of the depth to the width of the opening is large, a seed layer is formed on the surface of the uneven surface by the vapor phase deposition method, and then the seed layer is electroplated. By depositing a plating layer on top, the recesses can be filled with metal. Next, the outer surface of the formed metal film is polished and flattened so as to have a mirror surface. Polishing is preferably CMP (Chemical Mechanical). Polishing). The metal reflective film 12 may have an outer surface finished by polishing, or the surface may be mirrored on the surface of the polished metal film by a vapor deposition method or a wet method. A metal film may be deposited so as to be. The surface roughness (arithmetic mean roughness Ra) of the metal reflective film 12 to be a mirror surface is preferably 0.02 μm or less, and more preferably 0.01 μm or less.

The metal reflective film 12 preferably has at least a portion that functions as a reflective surface (a portion in contact with the translucent substrate 11A) formed of Ag, Al, or Rh having good reflectivity. The metal reflective film 12 may have a laminated structure. For example, a reflective layer made of Ag, Al or Rh and a seed layer made of Cr, Pt, Ni, Ti, Au, etc. are sequentially deposited and laminated on the portion in contact with the translucent substrate 11A by the vapor phase method, and then laminated. By electrolytic plating, a plating layer made of Au, Ni, Cu, Ag, etc. can be laminated on the seed layer. A solder layer or a eutectic alloy layer that can be used as an adhesive can also be formed on the outer surface of the metal reflective film 12. When the translucent substrate 11A is a conductive substrate (semiconductor substrate), the metal reflective film 12 can have a function as a negative electrode. In that case, at least a part of the metal reflective film in contact with the translucent substrate is formed of a metal forming ohmic contact with the translucent substrate.

Finally, a well-known method in this field such as dicing, scribing, and laser fusing is used to separate the LED element formed on the wafer into a chip. The LED element 10 also has an advantage that when the surface of the wafer on the metal reflective film 12 side is attached to the dicing tape in this step, the chip obtained by dividing the wafer does not easily fall off from the dicing tape. On the other hand, in the conventional LED element 100 shown in FIG. 7, since the outer surface of the metal reflective film 120 is an uneven surface, the adhesive force between this surface and the adhesive surface of the dicing tape is weak, and the wafer can be used. There is a problem that the chips obtained by dividing are easily dropped from the dicing tape.

(Embodiment 2) FIG. 2 is a cross-sectional view showing the structure of the LED element according to the second embodiment. The LED element 20 is formed by laminating a conductive translucent substrate 21A made of GaN, a translucent semiconductor layer 21B made of a nitride semiconductor, and a translucent electrode layer 21C made of ITO in this order. , Has a translucent plate-like body 21. A buffer layer (not shown) is preferably interposed between the translucent substrate 21A and the translucent semiconductor layer 21B. The translucent semiconductor layer 21B has an n-type layer 21B-1 and a p-type layer 21B-2 constituting a pn junction type light emitting device structure, and an active layer is preferably provided at the pn junction. .. The surface of the translucent electrode layer 21C, which is one of the main surfaces of the plate-shaped body 21, is made an uneven surface and is covered with a metal reflective film 22 that also serves as a positive electrode. The metal reflective film 22 is formed so as to fill the recesses on the surface of the translucent electrode layer 21C which is an uneven surface, and the outer surface thereof is flattened to be a mirror surface. A negative electrode 24 is formed on a part of the outer surface of the translucent substrate 21A. The LED element 21 is mounted at a junction down with the surface of the metal reflective film 22 facing the surface of the mounting destination member.

(Embodiment 3) FIG. 3 is a cross-sectional view showing the structure of the LED element according to the third embodiment. The LED element 30 is formed by laminating a conductive translucent substrate 31A made of GaN, a translucent semiconductor layer 31B made of a nitride semiconductor, and a translucent electrode layer 31C made of ITO in this order. , Has a translucent plate-like body 31. The translucent semiconductor layer 31B has an n-type layer 31B-1 and a p-type layer 31B-2 constituting a pn junction type light emitting device structure, and an active layer is preferably provided at the pn junction. .. The translucent electrode layer 31C is dispersed in a dot shape on the surface of the translucent semiconductor layer 31, and each dot has a truncated cone shape. As a result, one main surface of the plate-shaped body 31 is an uneven surface composed of the surface of the translucent semiconductor layer 31B and the surface of the translucent electrode layer 31C. A metal reflective film 32 that also serves as a positive electrode is formed so as to cover this uneven surface. The metal reflective film 32 is formed so as to fill the concave portion of the uneven surface, and its outer surface is flattened to be a mirror surface. A negative electrode 34 is formed on a part of the outer surface of the translucent substrate 31A. The LED element 31 is mounted at a junction down with the surface of the metal reflective film 32 facing the surface of the mounting destination member.

(Embodiment 4) FIG. 4 is a cross-sectional view showing the structure of the LED element according to the fourth embodiment. In this LED element 40, a conductive translucent substrate 41A made of GaN, a translucent semiconductor layer 41B made of a nitride semiconductor, and a translucent electrode layer 41C made of ITO are laminated in this order. , Has a translucent plate-like body 41. The translucent semiconductor layer 41B has an n-type layer 41B-1 and a p-type layer 41B-2 constituting a pn junction type light emitting device structure, and an active layer is preferably provided at the pn junction. .. An opening is formed in the translucent electrode layer 41C, and a recess having a V-shaped cross section is formed in the translucent semiconductor layer 41B by etching at the position of the opening. This recess has a depth that reaches the n-type layer 41B-1. The recess may be hole-shaped (conical hole or pyramidal hole) or groove-shaped (V-groove). The surface of the nitride semiconductor exposed in the recess is covered with a translucent insulating protective film (not shown). Examples of the material of the insulating protective film include silicon oxide, silicon nitride, silicon nitride, aluminum oxide, spinel, zirconium oxide, magnesium oxide, titanium oxide, magnesium fluoride, and lithium fluoride. As described above, one main surface of the plate-shaped body 41 is an uneven surface composed of the surface of the translucent insulating protective film and the surface of the translucent electrode layer 41C. A metal reflective film 42 that also serves as a positive electrode is formed so as to cover this uneven surface. The metal reflective film 42 is formed so as to fill the concave portion of the uneven surface, and its outer surface is flattened to be a mirror surface. A negative electrode 44 is formed on a part of the outer surface of the translucent substrate 41A. The LED element 41 is mounted at a junction down with the surface of the metal reflective film 42 facing the surface of the mounting destination member.

In the fourth embodiment, the cross-sectional shape of the recess formed at the position of the opening of the translucent semiconductor layer 41C may be V-shaped, trapezoidal, rectangular, semicircular, U-shaped, or any other shape. can do. The recess can be perforated or grooved in any cross-sectional shape. In the fourth embodiment, the translucent electrode 41C can be replaced with a translucent or impermeable electrode made of a metal film.

(Embodiment 5) FIG. 5 is a cross-sectional view showing the structure of the LED element according to the fifth embodiment. In this LED element 50, a translucent semiconductor layer 51B made of a nitride semiconductor and a conductive translucent substrate 51D made of ZnO bonded to the translucent semiconductor layer 51B as a support substrate are laminated. It has a translucent plate-like body 51. The translucent semiconductor layer 51B has an n-type layer 51B-1 and a p-type layer 51B-2 constituting a pn junction type light emitting device structure, and an active layer is preferably provided at the pn junction. .. The surface of the translucent substrate 51D, which is one of the main surfaces of the plate-shaped body 51, is an uneven surface and is covered with a metal reflective film 52 that also serves as a positive electrode. The metal reflective film 52 is formed so as to fill the recesses on the surface of the translucent substrate 51D which is an uneven surface, and the outer surface thereof is flattened to be a mirror surface. A negative electrode 54 is formed on a part of the outer surface of the n-type layer 51B-1.

In order to manufacture the LED element 50 shown in FIG. 5, first, the n-type layer 51B-1 and the p-type layer 51B-2 are vapor-deposited and laminated on a sapphire substrate via a buffer layer. Next, the translucent substrate 51D made of ZnO is bonded to the surface of the p-type layer 51B-2 by wafer bonding. Non-Patent Document 1 can be referred to for details of the joining method. After joining, the surface of the translucent substrate 51D is processed into an uneven surface, and a metal reflective film 52 covering the uneven surface is formed. Further, the sapphire substrate and the buffer layer are removed by using a method such as laser lift-off, polishing, and etching to expose the n-type layer 51B-1 and form a negative electrode 54 on the surface of the exposed n-type layer 51B-1. To do.

(Embodiment 6) FIG. 6 is a cross-sectional view showing the structure of the LED element according to the sixth embodiment. The LED element 60 is bonded to the conductive first translucent substrate 61A made of GaN, the translucent semiconductor layer 61B made of a nitride semiconductor, and the translucent semiconductor layer 61B as a support substrate. It has a translucent plate-like body 61 formed by laminating a second conductive translucent substrate 61D made of ZnO. The outer surface of the first translucent substrate 61A, which is one main surface of the plate-shaped body 61, is processed to be an uneven surface having a plurality of convex portions having a trapezoidal cross section. The convex portion may have a truncated cone shape (frustum, pyramidal cone) or a ridge shape having a flat top surface. A negative electrode 64 is formed on the top surface of each convex portion. A buffer layer (not shown) is preferably interposed between the first translucent substrate 61A and the translucent semiconductor layer 61B. The translucent semiconductor layer 61B has an n-type layer 61B-1 and a p-type layer 61B-2 constituting a pn junction type light emitting device structure, and an active layer is preferably provided at the pn junction. .. The surface of the second translucent substrate 61D, which is the other main surface of the plate-shaped body 61, is an uneven surface and is covered with a metal reflective film 62 that also serves as a positive electrode. The metal reflective film 62 is formed so as to fill the recesses on the surface of the translucent substrate 61D which is an uneven surface, and the outer surface thereof is flattened to be a mirror surface.

In the sixth embodiment, the height of the convex portion (height from the bottom of the concave portion to the top of the convex portion) formed on the surface of the first translucent substrate 61A is the first translucent substrate before processing. It can be as large as the thickness of 61A. Therefore, the height of the convex portion can be 50 μm or more, although it depends on the thickness of the first translucent substrate 61A before processing. As the height of the convex portion is increased, the probability that light is taken out from the side surface of the convex portion is increased, and the luminous efficiency of the element is improved. The cross-sectional shape of the convex portion can be any shape such as a rectangular shape, a semicircular shape, and a triangular shape, in addition to the trapezoidal shape. By forming electrodes on the respective surfaces of the convex portions provided on the surface of the first translucent substrate 61A, the current can be uniformly injected into the translucent semiconductor layer 61B. However, it is not essential to form the electrodes in this way. For example, the electrodes formed on the surface of the first translucent substrate 61A may be formed only on the surface of one of the plurality of convex portions. Alternatively, it may be formed on the surface of the concave portion of the uneven surface.

In order to manufacture the LED element 60 shown in FIG. 6, first, an n-type layer 61B-1 and a p-type layer 61B-2 are placed on a GaN substrate to be the first translucent substrate 61A via a buffer layer. The vapor phase is grown in order and laminated. Next, a second translucent substrate 61D made of ZnO is bonded to the surface of the p-type layer 61B-2 by wafer bonding. Non-Patent Document 1 can be referred to for details of the joining method. After joining, the surface of the second translucent substrate 61D is processed into an uneven surface, and a metal reflective film 62 covering the uneven surface is formed. Further, the surface of the first translucent substrate 61A is processed by etching or a mechanical method to obtain an uneven surface. Then, the negative electrode 64 is formed on the top surface of the convex portion of the first translucent substrate 61A which is made an uneven surface.

In the LED element 60 shown in FIG. 6, the difference in refractive index between the first translucent substrate 61A made of GaN and the translucent semiconductor layer 61B made of nitride semiconductor is small (or there is no difference in refractive index). Light traveling from the inside of the translucent semiconductor layer 61B toward the first translucent substrate 61A is hardly reflected at the interface between the translucent semiconductor layer 61B and the first translucent substrate 61A. .. The same can be said when a substrate having a higher refractive index than the translucent semiconductor layer 61B made of a nitride semiconductor (for example, a SiC substrate) is used as the first translucent substrate 61A. On the other hand, the second translucent substrate 61D made of ZnO has a lower refractive index than the translucent semiconductor layer 61B made of nitride semiconductor, so that the translucent semiconductor layer 61B and the second translucent substrate 61D Light incident from the translucent semiconductor layer 61B side with respect to the interface with the light is reflected at this interface due to the difference in refractive index. Therefore, in the LED element 60, there is a high probability that the light generated inside the translucent semiconductor layer 61B is taken out of the element from the surface on the first translucent substrate 61A side.

The present invention is not limited to the embodiments explicitly shown above, and various modifications can be made without departing from the spirit of the invention.

<figref num="1">It is sectional drawing which shows the structure of the light emitting diode element which concerns on embodiment of this invention.</figref><figref num="2">It is sectional drawing which shows the structure of the light emitting diode element which concerns on embodiment of this invention.</figref><figref num="3">It is sectional drawing which shows the structure of the light emitting diode element which concerns on embodiment of this invention.</figref><figref num="4">It is sectional drawing which shows the structure of the light emitting diode element which concerns on embodiment of this invention.</figref><figref num="5">It is sectional drawing which shows the structure of the light emitting diode element which concerns on embodiment of this invention.</figref><figref num="6">It is sectional drawing which shows the structure of the light emitting diode element which concerns on embodiment of this invention.</figref><figref num="7">It is sectional drawing which shows the structure of the conventional light emitting diode element.</figref>

Code description

10, 20, 30, 40, 50, 60 Light emitting diode elements 11, 21, 31, 41, 51, 61 Translucent plate-like bodies 11A, 21A, 31A, 41A, 51A, 61A Translucent substrates 11B, 21B , 31B, 41B, 51B, 61B Translucent semiconductor layer 11C, 21C, 31C, 41C Translucent electrode layer 51D, 61D Translucent substrate 12, 22, 32, 42, 52, 62 Metal reflective film 13 Negative electrode 14 , 24, 34, 44, 54, 64 Positive electrodes