JP2011243614A - Light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting device, having two electrodes formed on one side of a semiconductor light-emitting function layer, which obtains uniform intensity of light emission in the longitudinal direction.SOLUTION: A semiconductor light-emitting function layer 20, formed on an Si substrate 11, has a laminate structure comprising an n-type GaN layer (first semiconductor layer) 21, an MQW layer 22, and a p-type GaN layer (second semiconductor layer) 23. The p-type GaN layer 23 has a transparent electrode 31 formed on a surface (main surface on one side) thereof extending toward a right edge side from the other end (left edge) side. An n-side electrode 34 is formed in a region on the right edge side, and a p-side electrode 33 is formed in a region on the left edge side. The transparent electrode 31 expands in width from the left edge toward the right edge. This construction ensures that expansion of a current flowing through the MQW layer 22 in the vertical direction on a side thereof close to the p-side electrode 33 is limited by the transparent electrode 33.

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 for the transparent electrode 96 include ITO (Indium-Tin-Oxide), ZnO (Zinc-Oxide), and the like. .

  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, the light emitted to the upper side in FIG. 8 is blocked by the n-side electrode 95 at the left end portion of the semiconductor light emitting functional layer 91, but 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 shown by the dotted arrow in FIG.

  As described above, by using the transparent electrode as an electrode connected to one of the electrodes, the surface potential of the semiconductor light emitting functional layer 91 can be made uniform, and a light emitting element that emits light uniformly can be obtained. .

JP-A-61-85878

  If both the electrodes of the light emitting diode are connected to the upper and lower surfaces of the semiconductor light emitting functional layer, respectively, uniform light emission can be extracted with the above configuration. However, when both electrodes of the light emitting diode are formed on the same main surface side of the semiconductor light emitting functional layer (for example, the upper surface side of the semiconductor light emitting functional layer), it is difficult to obtain uniform light emission. This is more conspicuous as the distance between both electrodes becomes wider.

  FIG. 9 is a top view (a) in the case where the same configuration as in FIG. 8 is applied to a light emitting element 190 in which both electrodes are provided on one surface side of the semiconductor light emitting functional layer and an elongated configuration is provided between both electrodes. The sectional view (b) in the PP direction is shown. Here, the semiconductor light emitting functional layer 191 includes an n-type semiconductor layer 192 and a p-type semiconductor layer 193 thereon. At the right end, the p-type semiconductor layer 193 is removed to expose the n-type semiconductor layer 192, and an n-side electrode 194 is formed thereon. A p-type electrode 195 is formed on the p-type semiconductor layer 193 at the left end. Similar to FIG. 8, the transparent electrode 196 covers the p-side electrode 195 and is formed on the entire top surface of the p-type semiconductor layer 193. Although FIG. 9B is a cross-sectional view, hatching of each semiconductor layer is omitted for explanation.

  In this case, a current for causing the semiconductor light emitting functional layer 191 to emit light flows from the p-side electrode 195 side to the n-side electrode 194 side, as indicated by an arrow in FIG. There are various current paths during this period as indicated by arrows in FIG. 9B, for example. This is because the horizontal distance from the p-side electrode 195 to the n-side electrode 194 is wide, so that there are many components flowing in the transparent electrode 196, the p-type semiconductor layer 193, and the n-type semiconductor layer 192 in the horizontal direction. It is to become. In addition, since these layers are all thinner than this distance, the electric resistance against current flowing in these layers in the horizontal direction is high. On the other hand, a current that contributes to light emission is a current that passes through a pn junction (interface between the p-type semiconductor layer 193 and the n-type semiconductor layer 192) as indicated by a thick black arrow in FIG. 9B. Emits light indicated by a dotted arrow. This current intensity depends on the voltage drop when a voltage drop occurs due to a large resistance in the current path flowing in the horizontal direction. Since this voltage drop greatly depends on the current path, it is difficult to obtain uniform light emission intensity in the horizontal direction. For this reason, the non-uniformity of the emission intensity depends on the film thickness configuration of the transparent electrode 196, the p-type semiconductor layer 193, and the n-type semiconductor layer 192 and the resistivity of each layer. For example, when the semiconductor light emitting functional layer 191 is composed of gallium nitride (GaN), it is usual to sequentially form an n-type GaN layer and a p-type GaN layer on the epitaxial substrate. In this case, the resistance of the n-type GaN layer is low, and the resistance of the p-type GaN layer and the transparent electrode is higher than this. In such a case, the emission intensity is usually high near the p-side electrode 195 and the emission intensity is low near the n-side electrode 194. Such a problem does not occur when the resistance of the transparent electrode or the p-type GaN layer is negligible, but in practice, it is difficult to increase the conductivity of the material constituting the transparent electrode or the p-type GaN. It is difficult to make the resistance small enough to be ignored.

  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 in contact with 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. In the surface of the first electrode and the second semiconductor layer, the effective length in the direction perpendicular to the extending direction is extended from the other end side toward the one end side. , Long from the other end side toward the one end side And formed a transparent electrode to be on the side of the other end, characterized by comprising a second electrode formed on the transparent electrode in contact with the transparent electrode.
In the light-emitting element of the present invention, a light-emitting layer is formed on a first semiconductor layer having a first conductivity type, and a second conductivity having a conductivity type opposite to the first conductivity type is formed on the light-emitting layer. A semiconductor light emitting functional layer in which a second semiconductor layer having a mold is formed is used, and two electrodes used for energization for causing the semiconductor light emitting functional layer to emit light are both in the second semiconductor light emitting functional layer. A light-emitting element formed on a main surface on which a layer is formed, wherein the second semiconductor layer and the light-emitting layer are removed from the main surface side on one end side of the semiconductor light-emitting functional layer. The first electrode formed so as to be in contact with the first semiconductor layer and the surface of the second semiconductor layer from the other end side to the one end side. In the transparent electrode formed by stretching and the other end side, A second electrode formed on the transparent electrode so as to be in contact with the transparent electrode, wherein the second semiconductor layer is perpendicular to the direction from the other end toward the one end. An effective length in one direction is formed on the light emitting layer so as to increase from the other end toward the one end.
In the light emitting device of the present invention, an insulating layer is formed to cover the transparent electrode and the semiconductor light emitting functional layer, and the first electrode and the second electrode are respectively formed through the openings formed in the insulating layer. The first semiconductor layer is in contact with the transparent electrode.
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 first semiconductor layer is formed on a silicon substrate by epitaxial growth.
The light emitting device of the present invention is characterized in that side surfaces other than the end portions in the semiconductor light emitting functional layer are tapered.
In the light emitting device of the present invention, the ratio of the distance between the first electrode and the second electrode with respect to the width of the semiconductor light emitting functional layer in the direction perpendicular to the direction from the one end to the other end Is 10 or more.

  Since the present invention is configured as described above, a light emitting element having a structure in which two electrodes are formed on one surface of a semiconductor light emitting functional layer can obtain uniform light emission intensity in the longitudinal direction.

It is the top view (a) of the light emitting element which concerns on embodiment of this invention, and sectional drawing (b) in the AA direction. It is sectional drawing (a) in the BB direction of the light emitting element which concerns on embodiment of this invention, sectional drawing (b) in CC direction, and sectional drawing (c) in DD direction. It is a figure which shows two examples of the form at the time of using the light emitting element which concerns on embodiment of this invention. The top view (a) of the 1st modification of the light emitting element which concerns on embodiment of this invention, the sectional view in the EE direction (b), the sectional view in the FF direction (c), the GG direction It is sectional drawing in (d). It is the top view (a) of the 2nd modification of the light emitting element which concerns on embodiment of this invention, the sectional view (b) in the HH direction, and the sectional view (c) in the II direction. The top view (a) of the 3rd modification of the light emitting element which concerns on embodiment of this invention, sectional drawing (b) in the JJ direction, sectional drawing (c) in KK direction, LL direction It is sectional drawing in (d). The top view (a) of the 4th modification of the light emitting element which concerns on embodiment of this invention, the sectional view (b) in the MM direction, the sectional view (c) in the NN direction, OO direction It is sectional drawing in (d). 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 PP 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.

  FIG. 1 is a top view (a) of the light-emitting element 10 and a cross-sectional view (B) in the AA direction. 2A, 2B, and 2C are cross-sectional views in the BB direction, the CC direction, and the DD direction, respectively, in FIG.

  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.

  A transparent electrode 31 is formed on the surface (one main surface) of the p-type GaN layer 23 so as to extend from the other end (left end) to the right end. Furthermore, the insulating layer 32 is formed so as to cover the semiconductor light emitting functional layer 20 and the transparent electrode 31. Openings are formed in the insulating layer 32 at two locations, a region where the p-type GaN layer 23 and the MQW layer 22 are partially removed on the right end side and a region on the left end side. An n-side electrode (cathode: first electrode) 34 is formed in the region on the right end side, and a p-side electrode (anode: second electrode) 33 is formed in the region on the left end side. With this configuration, the n-side electrode 34 is connected to the n-type GaN layer 21, and the p-side electrode 33 is connected to the transparent electrode 31. The transparent electrode 31 and the n-side electrode 34 are not in contact with each other. In order to facilitate the description of the configuration, the illustration of the insulating layer 32 is omitted in FIG.

  Further, the end portions of the Si substrate 11 and the semiconductor light emitting functional layer 20 thereon are tapered as shown in FIG. The p-side electrode 33 and the n-side electrode 34 cover the tapered portion via the insulating layer 32. The above structure is formed on an insulating support substrate (not shown).

  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, the MQW layer 22, and the 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, taper angle (theta) 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 has a sufficient insulating property and is made of a material that is transparent to the light emitted from the light emitting element 10 (semiconductor light emitting functional layer 20). For example, the insulating layer 32 is made of silicon oxide (SiO ₂ ). For example, the CVD (Chemical Vapor Deposition) method or the like is used to form the stepped portion where the p-type GaN layer 23 and the MQW layer 22 are removed in the right end region or the 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.

  With this configuration, the p-side electrode 33 is connected to the p-type GaN layer 23 via the transparent electrode 31, and the n-side electrode 34 is directly connected to the n-type GaN layer 21. Thus, by applying a positive voltage to the p-side electrode 31 and a negative voltage to the n-side electrode 34, the light emitting layer (mainly the MQW layer 22) in the semiconductor light emitting functional layer 20 can emit light. This light is emitted directly from the surface of the p-type GaN layer 23 or through the transparent electrode 31 to the upper side in FIG.

  What is characteristic here is the width of the transparent electrode 31 (the length in the direction perpendicular to the direction in which the transparent electrode 31 extends), as shown in FIGS. 1 (a), 2 (a), (b), and (c). Is not uniform over the direction from the n-side electrode 34 to the p-side electrode 31 (left and right directions in FIG. 1) in the light emitting element 10. Specifically, the width increases from the left end (the other end: the side where the p-side electrode 33 is present) to the right end (the one end: the side where the n-side electrode 34 is present). Thereby, the spread of the current flowing in the vertical direction through the MQW layer 22 on the side close to the p-side electrode 33 is limited by the transparent electrode 31. Therefore, compared with the case where the transparent electrode 31 has a uniform width, the light emission intensity on the side close to the p-side electrode 33 can be lowered. Alternatively, the current flowing in the vertical direction through the MQW layer 22 on the side close to the n-side electrode 34 can be increased, and the emission intensity on the side close to the n-side electrode 34 can be increased.

  That is, the light emission intensity can be made uniform in the longitudinal direction of the light emitting element 10 (left and right direction in FIG. 1A). This effect is remarkable when the longitudinal non-uniformity of light emission becomes a problem, that is, when the distance between the p-side electrode 33 and the n-side electrode 34 in the light emitter 10 is wide and the light emitter 10 is long. Specifically, for example, when the ratio of the distance between the n-side electrode 34 and the p-side electrode 33 with respect to the width of the semiconductor light emitting functional layer 20 between the n-side electrode 34 and the p-side electrode 33 is 10 or more, it is particularly remarkable. It becomes. At this time, the width of the transparent electrode 31 is appropriately set so that the light emission intensity in the longitudinal direction is uniform. The optimum distribution of the width is determined by the current distribution flowing in the semiconductor light emitting functional layer 20 and the transparent electrode 31, and this is determined by the thickness, resistivity, etc. of the n-type GaN layer 21, the p-type GaN layer 23, and the transparent electrode 31. .

  In the configuration of FIG. 1, the p-side electrode 33 is formed on the transparent electrode 31, and the p-side electrode 33 and the p-type GaN layer 23 are not in direct contact with each other. As in the technique described in Patent Document 1, the vertical relationship between the p-side electrode 33 and the transparent electrode 31 is reversed, and the p-side electrode 33 and the p-type GaN layer 23 are in direct contact with each other at the left end. The current flowing directly from the p-side electrode 33 having a low electric resistance to the p-type GaN layer 23 is dominant, and the current component flowing from the transparent electrode 31 to the p-type GaN layer 23 is reduced. For this reason, the emission intensity in the vicinity of the p-side electrode 33 is particularly high, and the effect of uniformizing the emission intensity by changing the width of the transparent electrode 31 is reduced. That is, in order to obtain the above effect, the transparent electrode 31 is formed on the p-type GaN layer 23 and the p-side electrode 33 is formed on the transparent electrode 31 as shown in FIGS. A configuration is preferred.

  In the above example, all the side surfaces of the semiconductor light emitting functional layer 20 are tapered, and the tapered end portions are both covered with the p-side electrode 33 and the n-side electrode 34 via the insulating layer 32. . The main light emitting layer in the semiconductor light emitting functional layer 20 is the MQW layer 22. With this configuration, the end of the MQW layer 22 is shielded by the p-side electrode 33 and the n-side electrode 34. Also, with this configuration, part of light emitted obliquely upward and laterally from the light emitting layer is reflected by the tapered side surface and absorbed by the Si substrate 11 on the lower side. Accordingly, for example, when the light emitting elements 10 are arranged and used, it is possible to suppress the occurrence of light emission crosstalk between the adjacent light emitting elements 10. At this time, for example, the portion to be tapered can be set as appropriate. For example, only the side surfaces of the left and right end portions in FIGS. 1A and 1B may be tapered, and the other side surfaces (the side surfaces in FIGS. 2A, 2B, and 2C) may not be tapered. is there. In the case where a side surface that is not tapered is provided, the size of the light emitting element 10 in the direction in which the side surface is provided can be reduced. That is, the tapered portion can be only a portion where the crosstalk of light emission becomes a problem. Such a shape can be realized by separately performing the processing on the side surface to be tapered and the processing on the side surface not to be tapered.

  As an example in which the light-emitting element 10 having the configuration of FIGS. 1 and 2 is preferably used, there is a seven-segment display as shown in FIG. 3A and a one-dimensional light-emitting element array as shown in FIG. The 7-segment display can be preferably used as a display element, and the one-dimensional light-emitting element array can be preferably used as a display element or a light-emitting element for measurement. In such a case, the light emission intensity in each light emitting element can be made uniform in the length direction, and crosstalk between adjacent light emitting elements can be reduced.

  As long as the shape (pattern) of the transparent electrode 31 in the light-emitting element 10 can adjust the effective width of the transparent electrode 31 (effective length in a direction perpendicular to the extending direction (longitudinal direction) of the transparent electrode 31), It can be set as appropriate. 4A is a top view of a light emitting device 40 which is a first modification of the light emitting device 10 described above, FIG. 4B is a sectional view thereof in the EE direction, and FIG. 4C is a sectional view thereof in the FF direction. The sectional view (d) in the GG direction is shown. Note that a cross-sectional view corresponding to FIG. 1B of the light emitting element 40 is the same as that of FIG. In this configuration, the width of the transparent electrode 31 is gradually reduced from the n-side electrode 34 toward the p-side electrode 33. Obviously, the same effect can be obtained.

  In the above example, the entire width of the transparent electrode in the longitudinal direction of the light emitting element is changed. However, the effective length in the direction perpendicular to the longitudinal direction can be changed without changing the actual overall width. For example, the effective length can be changed by forming a gap inside the width direction without changing the entire width of the transparent electrode. FIG. 5 is a top view (a) of a light emitting device 50 as a second modification using this embodiment, a sectional view (b) in the HH direction, and a sectional view (c) in the II direction. Show. It is obvious that the same effect can be obtained with this configuration.

  The effective length can be changed by changing the overall width of the transparent electrode and providing a gap inside the width direction. FIG. 6 is a top view (a) of a light emitting device 60 as a third modification using this configuration, a sectional view (b) in the JJ direction, a sectional view (c) in the KK direction, The sectional view (d) in the LL direction is shown.

  Also, the same effect can be obtained by making the effective length in the direction perpendicular to the longitudinal direction of the transparent electrode constant and adjusting the width of the p-type GaN layer (second semiconductor layer) 23 instead. FIG. 7 is a top view (a) of a light emitting element 70 as a fourth modified example as an example of this configuration, a cross-sectional view in the MM direction (b), and a cross-sectional view in the NN direction (c). It is sectional drawing (d) of the OO direction. In this configuration, the width of the transparent electrode 31 (effective length in a direction perpendicular to the extending direction of the transparent electrode 31) is constant, and instead, a p-type GaN layer (second semiconductor layer) below the transparent electrode 31. The width 23 (effective length in a direction perpendicular to the extending direction of the transparent electrode 31) increases from the left end side toward the right end side. In this semiconductor light emitting functional layer 20, the actual light emitting layer is the MQW layer 22, and the p-type GaN layer 23 functions as a semiconductor layer connected to the light emitting layer. It is clear that Moreover, the form of the p-type GaN layer 23 can also be made the same as the form of the transparent electrode 31 in the first to third modifications. Or it is also possible to combine this structure with the 1st-3rd modification suitably.

  In addition to the above examples, the effective length in the direction perpendicular to the longitudinal direction of the transparent electrode and the p-type GaN layer (second semiconductor layer) is short on the p-side electrode (second electrode) side, and the n-side The form which becomes long on the electrode (first electrode) side can be appropriately set.

  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. If the conductivity at is low, it is clear that the same effect can be obtained even if these conductivity types are reversed. That is, the conductivity type of the first semiconductor layer and the second semiconductor layer is opposite, 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 addition, as described above, the end portion of the semiconductor light emitting functional layer can be tapered to suppress crosstalk. However, the uniform emission intensity in the longitudinal direction of the semiconductor light emitting functional layer can be achieved by the taper. Yes, with or without. In the case of a structure in which the tapered end portion is covered with an electrode, an insulating layer is indispensable in order to ensure insulation between the electrode at the end portion and each semiconductor layer and the light emitting layer. However, when this structure is not used, for example, the p-side electrode 33 is locally formed on the transparent electrode 31 at the left end in FIG. 1 without using the insulating layer, and the n-type GaN layer 21 is formed at the right end. It is also possible to locally form the n-side electrode 34 thereon.

10, 40, 50, 60, 70, 90, 190 Light-emitting element 11 Si substrate (substrate)
20, 91, 191 Semiconductor light emitting functional layer 21 n-type GaN layer (first semiconductor layer)
22 MQW layer (light emitting layer)
23 p-type GaN layer (second semiconductor layer)
31, 96, 196 Transparent electrode 32 Insulating layer 33, 94, 195 p-side electrode (second electrode)
34, 95, 194 n-side electrode (first electrode)
92, 193 p-type semiconductor layer 93, 192 n-type semiconductor layer

Claims (7)

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 in contact with 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;
On the surface of the second semiconductor layer, the effective length in the direction perpendicular to the extending direction extends from the other end side toward the one end side, A transparent electrode formed so as to be longer from the one end to the side,
A second electrode formed on the transparent electrode so as to be in contact with the transparent electrode on the other end side;
A light emitting element comprising: A light emitting layer is formed on a first semiconductor layer having a first conductivity type, and a second semiconductor having a second conductivity type that is opposite to the first conductivity type on the light emitting layer. A semiconductor light emitting functional layer in which a layer is formed is used, and two electrodes used for energization for causing the semiconductor light emitting functional layer to emit light are both on the side of the semiconductor light emitting functional layer on which the second semiconductor layer is formed. A light emitting device formed on a main surface,
The first semiconductor layer is formed to be in contact with the first semiconductor layer at a position where the second semiconductor layer and the light emitting layer are removed from the main surface side on one end side of the semiconductor light emitting functional layer. Electrodes,
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 in contact with the transparent electrode on the other end side;
The second semiconductor layer has an effective length in a direction perpendicular to the direction from the other end toward the one end so as to increase from the other end toward the one end. A light emitting element formed on the light emitting layer. An insulating layer is formed to cover the transparent electrode and the semiconductor light emitting functional layer,
3. The first electrode and the second electrode are in contact with the first semiconductor layer and the transparent electrode, respectively, through an opening formed in the insulating layer. Light emitting element.   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 device according to claim 3, wherein the light emitting device is covered.   5. The light-emitting element according to claim 1, wherein the first semiconductor layer is formed on a silicon substrate by epitaxial growth.   6. The light emitting device according to claim 1, wherein a side surface of the semiconductor light emitting functional layer other than the end portion is tapered.   The ratio of the distance between the first electrode and the second electrode with respect to the width of the semiconductor light emitting functional layer in the direction perpendicular to the direction from the one end to the other end is 10 or more. The light emitting device according to claim 1, wherein the light emitting device is characterized in that:

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