JP5617670B2 - Light emitting element - Google Patents

Description

  The present invention relates to a structure of a light emitting element that emits light using a semiconductor as a constituent material, and more particularly to a structure of a linear light emitting element.

  Semiconductor light emitting diodes (LEDs) are used for various purposes. For example, lighting equipment using this is expected to be replaced in the future because of low power consumption and low heat generation compared to conventional incandescent bulbs and fluorescent lamps. Here, the p-type semiconductor layer and the n-type semiconductor layer in the LED are usually formed by epitaxial growth, ion implantation, or the like. Therefore, the pn junction surface is formed in parallel with the surface of the semiconductor wafer, and the electrode connected to the p side and the electrode connected to the n side are distributed to the upper surface and the lower surface of this semiconductor layer. The light emitting element can emit light by passing a forward current of a pn junction between these electrodes. At this time, since the electrode is generally made of a metal that blocks this light, it is difficult to extract the light from the place where the electrode is formed. Further, if this current is not uniform within the light emitting element, uniform light emission cannot be obtained.

  A specific configuration of a light-emitting element that solves such a problem is described in Patent Document 1, for example. A cross-sectional view thereof is shown in FIG. The semiconductor light emitting functional layer 91 that emits light in the light emitting element 90 has a two-layer structure in which a p-type semiconductor layer 92 is provided on the lower side and an n-type semiconductor layer 93 is provided on the upper side. A p-side electrode 94 made of metal is formed on the entire lower surface of the semiconductor light emitting functional layer 91 (lower surface of the p-type semiconductor layer 92), and one surface of the upper surface of the semiconductor light emitting functional layer 91 (the upper surface of the n-type semiconductor layer 93). An n-side electrode 95 made of metal is formed on the part. Further, a transparent electrode 96 is formed on the entire upper surface so as to cover the n-side electrode 95. Examples of the material of the transparent electrode 96 include ITO (Indium-Tin-Oxide), ZnO (Zinc-Oxide), and the like, which are conductive and at the same time transparent to the light emitted from the light emitting element 90. .

  In this structure, a voltage for operating (light-emitting) the light emitting element 90 is applied between the p-side electrode 94 and the n-side electrode 95. At this time, the p-side electrode 94 is formed on the entire lower surface, and the n-side electrode 95 is connected to the transparent electrode 96 formed on the entire upper surface. Since the entire lower surface of the p-type semiconductor layer 92 is covered with the p-side electrode 94, the potential is uniform. In addition, since the potential of the entire upper surface of the n-type semiconductor layer 93 is substantially uniform due to the presence of the transparent electrode 96, the current in the semiconductor light emitting functional layer 91 flows substantially uniformly in the vertical direction (pn junction direction). . For this reason, uniform light emission can be obtained in the plane.

  At this time, although the light emitted upward in FIG. 10 is blocked by the n-side electrode 95 at the left end portion of the semiconductor light emitting functional layer 91, it passes through the transparent electrode 96 without being blocked in most regions. To do. For this reason, uniform light emission can be taken out as indicated by a dotted arrow in FIG.

  In this way, by using the transparent electrode as an electrode connected to one of the electrodes, the surface potential on both sides of the semiconductor light emitting functional layer 91 can be made uniform, and a light emitting element that emits light uniformly can be obtained. Can do.

  However, for example, when a GaN-based semiconductor is used, a structure in which an n-type semiconductor layer is epitaxially grown on an insulating substrate and a p-type semiconductor layer is epitaxially grown thereon is generally used. In this structure, it is difficult to realize the configuration of FIG. 10 unless the substrate is removed. For this reason, the structure which shows the top view (a) in FIG. 11 and the sectional view (b) in the QQ direction is used. Here, a light emitting element having an elongated shape on the left and right is shown.

  In this structure, a semiconductor light emitting functional layer 190 is formed on an insulating substrate 180. The semiconductor light emitting functional layer 190 includes an n type semiconductor layer 191, a light emitting layer 192 thereon, and a p type semiconductor layer 193. At the right end, the p-type semiconductor layer 193 and the light emitting layer 192 are partially removed. The transparent electrode 194 is formed on the p-type semiconductor layer 193 in most of the central portion of this structure. Furthermore, an insulating layer 195 is formed on the entire surface. In the insulating layer 195, an opening reaching the p-type semiconductor layer 193 is formed on the left side, and an opening reaching the n-type semiconductor layer 191 is formed on the right side. A p-side electrode 196 is formed on the left side and an n-side electrode 197 is formed on the right side so as to cover these openings. Note that the insulating layer 195 is not shown in the top view (FIG. 11A).

  In this structure, a current can be passed through the light emitting layer 192 between the p-type semiconductor layer 193 and the n-type semiconductor layer 191, and light is emitted through the transparent electrode 194 in the entire region indicated by W in FIG. Can be taken out. However, in general, the electrical resistivity of the transparent electrode 194 and the p-type semiconductor layer 193 is lower than that of the n-type semiconductor layer 191, the p-side electrode 196, and the n-side electrode 197. Further, it is difficult to increase the thickness of the p-type semiconductor layer 193. For this reason, in the current path from the p-side electrode 196 to the n-side electrode 197, the electrical resistance of the transparent electrode 194 and the p-type semiconductor layer 193, or the voltage drop caused thereby cannot be ignored. In this case, it is difficult to make the current flowing through the light emitting layer 192 uniform in the left-right direction in FIG. 11, and light emission in this direction is uneven. Experimentally, the light emission is the strongest at the right side near the n-side electrode 197.

  In order to eliminate such non-uniformity, FIG. 12A is a top view of a structure in which the p-side electrode 196 is elongated in the right direction, and FIG. 12B is a cross-sectional view in the RR direction. In this structure, the p-side electrode 196 is elongated in the right direction, and contacts are made with the transparent electrode 194 at a plurality of locations, whereby the electrical resistance between the p-side electrode 196 and the p-type semiconductor layer 193 is reduced. The potential of the p-type semiconductor layer 193 is made uniform by decreasing. Further, although the p-side electrode 196 is opaque to light emission, the width of the light on the light emitting region is narrowed in the vertical direction in FIG. 12, thereby reducing the amount of light blocked by this.

  In addition, when using such a light emitting element in a one-dimensional or two-dimensional array, not only the uniformity of light emission in the light emitting element is improved, but also crosstalk between adjacent light emitting elements does not occur. It is also necessary to do so. For this purpose, Patent Document 2 describes a technique for shielding light by covering the side surface with the p-side electrode and the n-side electrode through an insulating layer.

JP-A-61-85878 Japanese Patent Laid-Open No. 11-74565

  However, since the influence of the electrical resistance in the p-type semiconductor layer 193 cannot be ignored, it is difficult to eliminate the non-uniformity of light emission in the longitudinal direction even when the configuration of FIG. 12 is used. In particular, in the case where the aspect ratio of the light emitting region has a large aspect ratio of 1: 100, such non-uniformity becomes remarkable. In the technique described in Patent Document 2, although the light emitted from the side surface can be suppressed, the nonuniformity of the light emitted upward cannot be improved.

  That is, it is difficult to obtain a uniform light emission intensity in the longitudinal direction in a light emitting device having two electrodes formed on one surface of the semiconductor light emitting functional layer. Such a problem is particularly noticeable when the distance between the two electrodes is wide.

  The present invention has been made in view of such problems, and an object thereof is to provide an invention that solves the above problems.

In order to solve the above problems, the present invention has the following configurations.
In the light-emitting element of the present invention, a second semiconductor layer having a second conductivity type, which is a conductivity type opposite to the first conductivity type, is formed on a first semiconductor layer having a first conductivity type. The semiconductor light emitting functional layer is used, and two electrodes used for energization for causing the semiconductor light emitting functional layer to emit light are both on the main surface of the semiconductor light emitting functional layer on the side where the second semiconductor layer is formed. A formed light-emitting element formed so as to be connected to the first semiconductor layer at a position where the second semiconductor layer is removed from the main surface side at one end of the semiconductor light-emitting functional layer. A first electrode formed on the surface of the second semiconductor layer, a transparent electrode formed by extending from the other end side toward the one end portion, and the other end portion. On the side of the transparent electrode so as to connect with the transparent electrode A second electrode which is the comprises the transparent electrode and the semiconductor light-emitting functional layer overlying formed insulating layer, wherein the first electrode, the second electrode is formed on the insulating layer The first electrode is connected to the first semiconductor layer and the transparent electrode through the openings, and a part of the second electrode extends from the other end side toward the one end side. Formed and connected to the transparent electrode at the stretched portion, the first electrode is not in contact with the second electrode, and a part of the second electrode is at the one end It is characterized by having a shape extending toward the other end portion rather than the tip end portion of the portion extending toward the portion .
In the light emitting device of the present invention, an end portion of the semiconductor light emitting functional layer is tapered, and at least one of the first electrode and the second electrode is an end portion of the semiconductor light emitting functional layer tapered. Is covered with the insulating layer .
In the light emitting device of the present invention, the portion where the second semiconductor layer is removed from the main surface side at one end of the semiconductor light emitting functional layer is such that the first semiconductor layer is exposed at the bottom. An opening formed in the semiconductor light emitting functional layer, wherein the first electrode is connected to the first semiconductor layer at the bottom.
In the light emitting device of the present invention, the first semiconductor layer is formed on a silicon substrate by epitaxial growth.
In the light emitting device of the present invention, the first semiconductor layer is made of an n-type nitride semiconductor, and the second semiconductor layer is made of a p-type nitride semiconductor.

  Since this invention is comprised as mentioned above, in the light emitting element of the structure which formed two electrodes in one surface of a semiconductor light-emitting functional layer, uniform luminescence intensity can be obtained in a longitudinal direction.

It is the top view (a) of the light emitting element which concerns on the 1st Embodiment of this invention, and sectional drawing (b) in the AA direction. Sectional view in the BB direction of the light emitting device according to the first embodiment of the present invention (a), sectional view in the CC direction (b), sectional view in the DD direction (c), EE It is sectional drawing (d) in a direction, and sectional drawing (e) in a FF direction. It is the top view (a) of the light emitting element which concerns on the 2nd Embodiment of this invention, and sectional drawing (b) in the GG direction. It is sectional drawing (a) in the HH direction of the light emitting element concerning the 2nd Embodiment of this invention, sectional drawing (b) in II direction, and sectional drawing (c) in JJ direction. It is the top view (a) of the light emitting element which concerns on the 3rd Embodiment of this invention, and sectional drawing (b) in the KK direction. It is sectional drawing (a) in the LL direction of the light emitting element which concerns on the 3rd Embodiment of this invention, and sectional drawing (b) in the MM direction. It is the top view (a) of the light emitting element which concerns on the 4th Embodiment of this invention, and sectional drawing (b) in the NN direction. It is sectional drawing in the OO direction of the light emitting element which concerns on the 4th Embodiment of this invention. It is the top view (a) of the light emitting element which concerns on the 5th Embodiment of this invention, and sectional drawing (b) in the PP direction. It is sectional drawing of an example of the conventional light emitting element. It is the top view (a) of an example of the conventional light emitting element which formed both the electrodes in the one main surface side, and sectional drawing (b) in the QQ direction. It is the top view (a) of other examples of the conventional light emitting element which formed both the electrodes in the one main surface side, and sectional drawing (b) in the RR direction.

  Hereinafter, a light-emitting element according to an embodiment of the present invention will be described. In this light emitting element, a p-side electrode (anode) and an n-side electrode (cathode) are both formed on one main surface side of the semiconductor light emitting functional layer. The semiconductor light emitting functional layer has an elongated shape, particularly in the direction from the p-side electrode to the n-side electrode.

(First embodiment)
FIG. 1A is a top view of a light emitting device 10 according to the first embodiment, and FIG. 1B is a cross-sectional view in the AA direction. 2A to 2E are cross-sectional views in the BB direction, CC direction, DD direction, EE direction, and FF direction in FIG. 1A, respectively.

  The semiconductor light emitting functional layer 20 that emits light in the light emitting element 10 is formed on the Si substrate 11, and includes an n-type GaN layer (first semiconductor layer) 21, an MQW (Multi Quantum Well) layer 22, and a p-type GaN layer (first layer). 2 semiconductor layers) 23. The main light emitting layer in this configuration is the MQW layer 22. In the region on one end (right end) side in FIG. 1B, the p-type GaN layer 23 and the MQW layer 22 are partially removed. Therefore, the right end of the semiconductor light emitting functional layer 20 that contributes to light emission is at the position indicated by T in FIG. 1B and FIG. 2, in this structure, in this structure, the Si substrate 11, the n-type GaN layer 21, the MQW layer 22, the p-type GaN layer 23, and a stacked layer composed of these layers. The end of the structure is tapered. Although not shown, the entire structure of FIG. 1 is formed on a support substrate.

  On the surface (one main surface) of the p-type GaN layer 23, the right end portion (position T) of the p-type GaN layer 23 extends from the other end portion (left end portion) side to the right end portion side. The transparent electrode 31 is formed to the vicinity. Further, an insulating layer 32 is formed so as to cover the entire structure. In two places, a region on the left end side (location of the cross section BB) and a region where the p-type GaN layer 23 and the MQW layer 22 are partially removed on the right end side (location of the cross section FF), An opening is formed in the insulating layer 32. In addition, smaller openings are formed in the insulating layer 32 at seven locations on the transparent electrode 31 between them (for example, at the section DD). In the top view (FIG. 1A), the insulating layer 32 is not shown.

  A p-side electrode (anode: second electrode) 33 is connected to the left end region. In addition, a region extending partially to the right side of the p-side electrode 33 is also connected to these seven regions. The p-side electrode 33 is made of a metal material that is not transparent to light emission but has a low electrical resistivity. As shown in the top view (FIG. 1A), the p-side electrode 33 includes the entire semiconductor light emitting functional layer 20 including the tapered end portion in the left region through the insulating layer 32. It is formed to cover. On the other hand, the partially extended region in the region on the right side of this is formed thinner than the transparent electrode 31 in the vertical direction in FIG. 1A, and is slightly thickened only in the opening portion. . FIG. 2 (b) shows a cross section of the stretched region that is not on the opening (section of the section CC), and FIG. 2 (c) shows a cross section of the section on the opening (section of the section DD). .

  On the other hand, the n-side electrode (first electrode: cathode) 34 is connected to the n-type GaN layer 21 at the section FF, and the transparent electrode 31, the p-side electrode 33, and the n-side electrode 34 are not in contact with each other. It is supposed to be configured. Similarly to the p-side electrode 33 in the left region, the n-side electrode 34 is formed so as to cover the entire laminated structure including the semiconductor light emitting functional layer 20 in the right region, including its tapered end face. Yes.

  Further, the n-side electrode 34 is a region on the left side of the region where the p-type GaN layer 23 and the MQW layer 22 are partially removed, that is, the right end portion of the semiconductor light emitting functional layer 20 in FIG. The upper surface of the light emitting functional layer 20 on the left side is also covered beyond (the position of T in (a)).

  Here, the Si substrate 11 is a silicon single crystal substrate, and may be doped with impurities to be highly conductive, or may be non-doped and have a high resistivity. The plane orientation is appropriately set so that a high-quality semiconductor light emitting functional layer 20 (n-type GaN layer 21, MQW layer 22, p-type GaN layer 23) can be heteroepitaxially grown thereon.

  The n-type GaN layer 21, MQW layer 22, and p-type GaN layer 23 can be epitaxially grown on the Si substrate 11 by MBE (Molecular Beam Epitaxy) method or MOCVD (Metal Organic Chemical Vapor Deposition) method. The n-type GaN layer 21 is appropriately doped with an impurity serving as a donor, and the p-type GaN layer 23 is appropriately doped with an impurity serving as an acceptor. The thickness of the n-type GaN layer 21 can be set to, for example, 5.0 μm, and the thickness of the p-type GaN layer 23 can be set to, for example, about 0.2 μm. The MQW layer 22 has a structure in which a plurality of InGaN and GaN thin films having a thickness of, for example, several nm to several tens of nm are stacked, and each of the InGaN and GaN layers is similar to the n-type GaN layer 21 and the p-type GaN layer 23. It is formed by epitaxial growth.

  In order to remove the p-type GaN layer 23 and the MQW layer 22 in the right end region of the semiconductor light emitting functional layer 20 and expose the n-type GaN layer 21, a photoresist is formed outside this region, and this is used as a mask. Perform dry etching. Further, the step of processing the semiconductor light emitting functional layer 20 into the form of FIG. 1 and tapering the end portion is performed by forming a tapered photoresist after forming the semiconductor light emitting functional layer 20 in the above order. This is performed by dry etching using this as a mask. The taper of the photoresist can be performed by adjusting exposure conditions and development conditions. Thereby, the taper angle of the edge part shown by FIG.1 (b) can be 30-60 degrees, for example.

  For example, ITO (Indium-Tin-Oxide) or ZnO (Zinc-Oxide) is used as the transparent electrode 31 as a material that can make ohmic contact with the p-type GaN layer 23 and is transparent to the light emitted from the semiconductor light emitting functional layer 20. Etc. In order to improve the ohmic property and adhesion between the p-type GaN layer 23, a titanium (Ti) layer or nickel (Ni) layer that is thin enough to transmit light is inserted between them. You can also. The patterning of the transparent electrode 31 is performed by forming the transparent electrode material on the entire surface, forming a mask such as a photoresist at a desired location, and then etching to remove the transparent electrode material other than the desired location (etching). Method), (2) A transparent electrode material other than the desired location is formed by forming the above transparent electrode material on the entire surface after forming a mask such as a photoresist other than the desired location, and then removing the mask later. Any method of removing (lift-off method) can be used. In addition, since the material which comprises the transparent electrode 31 requires high light transmittance, the electrical conductivity is lower than the material which comprises the p-side electrode 33 and the n-side electrode 34. For this reason, the electrical resistance of the transparent electrode 31 in the left-right direction in FIG. 1 is generally higher than that of the p-side electrode 33 and the n-side electrode 34.

The insulating layer 32 is made of a material that has sufficient insulating properties and is transparent to light emitted from the light emitting element 10 (semiconductor light emitting functional layer 20), and is made of, for example, silicon oxide (SiO ₂ ). For example, by using a CVD (Chemical Vapor Deposition) method or the like, the formation is also performed at a step portion where the p-type GaN layer 23 and the MQW layer 22 are removed in the right end region or at a tapered end portion. This can be formed with good coverage.

  The p-side electrode 33 is made of a highly conductive metal such as aluminum (Al). The n-side electrode 34 is made of a material that can make ohmic contact with the n-type GaN layer 21. The p-side electrode 33 and the n-side electrode 34 can be patterned in the same manner as the patterning of the transparent electrode 31. The material constituting the p-side electrode 33 and the n-side electrode 34 is not required to have high light transmittance. For this reason, these electrical conductivity can be made higher than the transparent electrode material which comprises the transparent electrode 31, and the electrical resistance (or voltage drop by these) in the p side electrode 33 and the n side electrode 34 can be disregarded. it can. On the other hand, the light emitted from the semiconductor light emitting functional layer 20 does not pass through the p-side electrode 33 and the n-side electrode 34.

  1, the electrical connection between the p-side electrode 33 and the transparent electrode 31 can be made in a wide range in the left-right direction in FIG. Electric resistance can be reduced. Thereby, the electrical resistance between the p-side electrode 33 and the p-type GaN layer 23 can also be reduced, and the uniformity of light emission in the left-right direction (longitudinal direction) can be enhanced. Here, the light from the light emitting layer is blocked by the p-side electrode 33 extending to the right side, but since this extended region is thin in the vertical direction, the amount of blocking can be reduced. This is the same as the structure of FIG.

  At this time, light emission from the semiconductor light emitting functional layer 20 is blocked in a region where the p-side electrode 33 and the n-side electrode 34 are formed on the semiconductor light emitting functional layer 20. On the other hand, light is emitted from the region where the p-side electrode 33 and the n-side electrode 34 are not formed on the semiconductor light emitting functional layer 20 toward the upper side in FIG.

  Due to the configuration of the p-side electrode 33, the uniformity of light emission in the longitudinal direction is enhanced. However, even in this case, generally, light emission on the side close to the contact region (opening) with the n-side electrode 34 in the semiconductor light emitting functional layer 20 is the strongest. In the structure of FIG. 1, since the region where the light emission is the strongest is particularly covered by the n-side electrode 34, uniform light emission can be obtained over the longitudinal direction. In general, it is effective that the length of the n-side electrode 34 covering the semiconductor light emitting functional layer 20 (transparent electrode 31) from the right end is about 100 μm or more. In this region, the light emitted from the semiconductor light emitting functional layer 20 toward the upper side in FIG. 1B is blocked by the n-side electrode 34 and reflected downward. Thereafter, it is absorbed in the Si substrate 11 made of silicon having a narrower forbidden band than GaN.

  Further, light emitted from the right, upper, and lower end faces of the right side region of the semiconductor light emitting functional layer 20 is also reflected and absorbed by the n-side electrode 34 covering the end portions. At this time, similarly to the light emitted upward in FIG. 1B, this light also becomes strong in the region on the right side of the semiconductor light emitting functional layer 20. When this light emitting element 10 is used as an array, this light is not preferable because it is difficult to distinguish it from light emitted from adjacent elements. That is, this effect is also reduced by the above structure. Similarly, light emitted from the left side, upper side, and lower side surfaces of the left region of the semiconductor light emitting functional layer 20 in FIG. 1A is reflected and absorbed by the p-side electrode 33 covering the end. By tapering the end surface of the semiconductor light emitting functional layer 20 / Si substrate 11 as described above, the coverage of these side surfaces of the p-side electrode 33 and the n-side electrode 34 can be improved.

  In the above configuration, the n-side electrode 34 covered the semiconductor light emitting functional layer 20 (p-type GaN layer 23) from the right end T to the vicinity of the right end of the p-side electrode 33. However, as long as the uniformity of light emission in the left-right direction (longitudinal direction) can be obtained, the range covering this can be set as appropriate, particularly on the left side. Generally, the emission intensity is highest around the right end of the transparent electrode 31 (one end of the transparent electrode 31 on one end side). In this case, at least the upper portion of the p-type GaN layer 23 in the region including the right end portion of the transparent electrode 31 only needs to be covered with the n-side electrode 34 via the insulating layer 32.

(Second Embodiment)
3A is a top view of the light emitting device 110 according to the second embodiment, and FIG. 3B is a cross-sectional view in the GG direction. 4A to 4C are cross-sectional views in the HH direction, the II direction, and the JJ direction in FIG. 3A, respectively. Since the Si substrate 11, the semiconductor light emitting functional layer 20, and the like constituting this are the same as those in the first embodiment, the description thereof is omitted (the same applies to the following embodiments). The same applies to the right end portion of the semiconductor light emitting functional layer 20 in FIG. In addition, the structure of the part corresponding to the cross section of the BB direction in FIG. 1, CC direction, DD direction, and FF direction is the same as that of 1st Embodiment.

  In the light emitting element 110, the n-side electrode 34 is not formed on the left side of the right end portion T of the semiconductor light emitting functional layer 20. That is, the light emitted from the semiconductor light emitting functional layer 20 is not blocked by the n-side electrode 34.

  Instead, in the light emitting element 110, the right end portion of the p-side electrode 33 greatly expands, exceeds the right end portion T of the semiconductor light emitting functional layer 20, and near the right end portion of the semiconductor light emitting functional layer 20 and FIG. The upper, lower and right side surfaces in a) are covered. Thereby, similarly to the first embodiment, light emission from a region with high light emission intensity is blocked by the p-side electrode 33, and uniform light emission can be obtained in the longitudinal direction. Similarly, a high heat dissipation effect can be obtained. The range in which the p-side electrode 33 should cover the p-type GaN layer 23 (semiconductor light emitting functional layer 20) is the same as in the first embodiment.

(Third embodiment)
FIG. 5A is a top view of a light emitting device 210 according to the third embodiment, and FIG. 5B is a cross-sectional view in the KK direction. 6 (a) and 6 (b) are cross-sectional views in the LL direction and the MM direction in FIG. 5 (a), respectively. In addition, the structure of the portion corresponding to the cross sections in the BB direction, the CC direction, and the DD direction in FIG. 1 is the same as that of the first embodiment.

  In the light emitting element 210, the structure of the semiconductor light emitting functional layer 20 and the like particularly in the right region is greatly different from that of the above embodiment. First, in the above-described embodiment, the MQW layer 22 and the p-type GaN layer 23 on the n-type GaN layer 21 are uniformly removed in the vicinity of the right end portion. These are removed locally only in the n-type GaN layer exposed region 212. That is, in this region in the semiconductor light emitting functional layer 20, the n-type GaN layer 21 forms an opening exposed at the bottom. Thereafter, an opening is formed in the insulating layer 32 in the n-side contact region 213 included in the opening, and an n-side electrode 34 is formed thereon, whereby the n-side electrode 34 and the n-type GaN layer are formed at the bottom. 21 is connected. The planar shape of the n-side electrode 34 is the same as that in the first embodiment, and the n-side electrode 34 also covers the left side of the n-type GaN exposed region 212. The structure and form of the p-side electrode 33 are the same as those in the first embodiment.

  Also in this structure, the n-side electrode 34 covers the space between the right end portion of the transparent electrode 31 and the portion where the p-type GaN layer 23 is removed from the main surface side where the emission intensity is highest. For this reason, as in the first embodiment, uniform light emission can be obtained over the longitudinal direction. In the case of this structure, the p-type GaN layer 21, the transparent electrode 31, etc. are also left over a wide region other than the n-type GaN layer exposed region 212, and the n-side electrode 34 around the n-side contact region 213 is left. Since the surface area is also increased, the heat dissipation effect can be particularly enhanced.

(Fourth embodiment)
FIG. 7A is a top view of a light emitting device 310 according to the fourth embodiment, and FIG. 7B is a cross-sectional view in the NN direction. FIG. 8 is a cross-sectional view in the OO direction in FIG. Further, the structure of the portion corresponding to the cross section in the BB direction, CC direction, DD direction, EE direction, and FF direction in FIG. 1 is the same as that of the first embodiment. .

  In the light emitting element 310, as compared with the light emitting element 10 of the first embodiment, the n-side electrode 34 has a shape extending to the left side and a shape surrounding the right end portion of the p-side electrode 33. That is, the n-side electrode 34 is not in contact with the p-side electrode 33, and is located on the left side (the other end) of the portion where the part of the p-side electrode 33 extends toward the right side (one end side). Part side).

  In this structure, as compared with the first to third embodiments, the region shielded by the n-side electrode 34 can be expanded to the left side, so that more uniform light emission can be obtained. . Further, since the area of the n-side electrode 34 is increased, the heat dissipation effect due to this is further increased.

(Fifth embodiment)
FIG. 9A is a top view of a light emitting element 410 according to the fifth embodiment, and FIG. 9B is a cross-sectional view in the PP direction. In the light emitting element 410, unlike the light emitting elements according to the first to fourth embodiments, the direction from the p-side electrode 33 to the n-side electrode 34 is not the longitudinal direction, and the direction perpendicular thereto is the longitudinal direction. It has become. The shape of the p-side electrode 33 is the same as that of the p-side electrode 94 in FIG. 10 and is not a shape that extends toward the n-side electrode 34.

  FIG. 9B is a sectional view in the longitudinal direction, and this structure is the same as that in FIG. In other words, the n-side electrode 34 extends to the p-side electrode side 33 from the end T of the semiconductor light emitting functional layer 20, thereby shielding a portion having a high light emission intensity.

  Thus, even when the direction from the p-side electrode toward the n-side electrode is not the longitudinal direction, a similar structure can be employed. This also increases the heat dissipation effect.

  It is obvious that the structures according to the first to fifth embodiments can be used in appropriate combination.

  In addition to the above example, in the region between one end side of the semiconductor light emitting functional layer (the side opposite to the side on which the p-side electrode is formed) and the transparent electrode end, the n-side electrode or the p-side electrode is It is obvious that the same effect can be obtained if the surface of the semiconductor light emitting functional layer is covered via the insulating layer. In this case, it is preferable to reduce the area where the n-side electrode or the p-side electrode covers the light emitting region other than this region and to prevent the light emission outside this region from being hindered. The shape of the n-side electrode or the p-side electrode can be appropriately set in addition to the above example.

  Further, in the above configuration, on the Si substrate 11, as the semiconductor light emitting functional layer 20, the n-type GaN layer 21 as the first semiconductor layer, the MQW layer 22 as the light emitting layer, and the p-type GaN layer as the second semiconductor layer. An example in which 23 was formed is described. However, even when the MQW layer 22 is not used, it is obvious that the device operates as a light emitting diode (LED) using a simple pn junction. Alternatively, a light emitting layer having a structure other than the MQW layer having the above structure can be used. In addition, the semiconductor light emitting functional layer can be made of a material other than GaN. In this case, a semiconductor material can be set according to the emission wavelength.

  In the above example, the n-type semiconductor layer (first semiconductor layer) is formed on the substrate (Si substrate 11) side, and the p-type semiconductor layer (second semiconductor layer) is formed thereon. It is clear that the same effect can be obtained even when these conductivity types are reversed when the conductivity at is low. That is, the first semiconductor layer and the second semiconductor layer have opposite conductivity types, and two electrodes connected to these semiconductor layers are formed on one main surface side of the semiconductor light emitting functional layer. For example, the above configuration is effective.

  Further, it is clear that the above-described effect can be obtained even if the semiconductor light emitting functional layer is not formed on the substrate. When a substrate is used, a buffer layer for enhancing the crystallinity of the semiconductor light emitting functional layer can be inserted between the substrate and the semiconductor light emitting functional layer. As long as the two electrodes are formed on the same main surface side of the semiconductor light emitting functional layer, the substrate and the buffer layer may be insulative or conductive.

  In the epitaxial growth, the above configuration is particularly effective in a structure in which an n-type layer having high conductivity is first formed on a substrate and a p-type layer having low conductivity and a transparent electrode are formed thereon. It is clear. Such a configuration is particularly prominent in nitride semiconductors including GaN as described above, and thus the above configuration is particularly effective in a light-emitting element using this material.

  In the above example, the end of the semiconductor light emitting functional layer or the like has a tapered shape and is covered with an n-side electrode or a p-side electrode through an insulating layer. However, such a configuration is not necessary when light leakage from the end face can be ignored. That is, it is not necessary for the n-side electrode and the p-side electrode to cover these end faces. In this case, it is not necessary that the end is tapered. In this case, an insulating layer other than the portion where the semiconductor light emitting functional layer is covered with the electrode is not necessarily required.

10, 90, 110, 210, 310, 410 Light-emitting element 11 Si substrate (substrate)
20, 91, 190 Semiconductor light emitting functional layer 21 n-type GaN layer (first semiconductor layer)
22, 192 MQW layer (light emitting layer)
23 p-type GaN layer (second semiconductor layer)
31, 96, 194 Transparent electrode 32, 195 Insulating layer 33, 94, 196 p-side electrode (second electrode)
34, 95, 197 n-side electrode (first electrode)
92, 193 p-type semiconductor layer 93, 191 n-type semiconductor layer 212 n-type GaN layer exposed region 213 n-side contact region

Claims (5)

A semiconductor light emitting functional layer is used in which a second semiconductor layer having a second conductivity type opposite to the first conductivity type is formed on a first semiconductor layer having a first conductivity type. The two electrodes used for energization for causing the semiconductor light emitting functional layer to emit light are both light emitting elements formed on the main surface of the semiconductor light emitting functional layer on the side where the second semiconductor layer is formed. And
A first electrode formed so as to be connected to the first semiconductor layer at a position where the second semiconductor layer is removed from the main surface side at one end of the semiconductor light emitting functional layer;
A transparent electrode formed on the surface of the second semiconductor layer by extending from the other end side toward the one end side;
A second electrode formed on the transparent electrode so as to be connected to the transparent electrode on the other end side;
An insulating layer formed to cover the transparent electrode and the semiconductor light emitting functional layer;
Comprising
The first electrode and the second electrode are respectively connected to the first semiconductor layer and the transparent electrode through an opening formed in the insulating layer,
A part of the second electrode is formed by extending from the other end side toward the one end side, and is connected to the transparent electrode at a portion formed by the extension,
The first electrode is not in contact with the second electrode, and a part of the second electrode is closer to the other end than a tip of a part extending toward the one end. A light-emitting element having a shape extending toward the surface . An end of the semiconductor light emitting functional layer is tapered, and at least one of the first electrode and the second electrode is connected to the end of the tapered semiconductor light emitting functional layer via the insulating layer. The light-emitting element according to claim 1 , wherein the light-emitting element is covered. The portion where the second semiconductor layer is removed from the main surface side at one end of the semiconductor light emitting functional layer is formed in the semiconductor light emitting functional layer so that the first semiconductor layer is exposed at the bottom. Opening.
The first electrode, the light emitting device according to claim 1 or 2, characterized in that it is connected to the first semiconductor layer at the bottom. It said first semiconductor layer, the light emitting device according to any one of claims 1 to 3, characterized in that formed on a silicon substrate by epitaxial growth. Said first semiconductor layer is composed of n-type nitride semiconductor, the second semiconductor layer is any one of the preceding claims, characterized in that it is constituted by a p-type nitride semiconductor to claim 4 The light emitting element as described in.

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