JP2008159957A - Semiconductor light-emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a homogeneous and efficient semiconductor light-emitting elements for a long lifetime by avoiding breakage of a semiconductor layer and an electrode, while realizing both a high output and high luminance, even when a high current is passed, without generating a region with the current concentrating in the semiconductor layer or the electrode, regardless of the composition of the semiconductor layer, film thickness, shape, conduction type, resistance value, or the like. <P>SOLUTION: The semiconductor light-emitting element comprises first and second electrodes each on first and second conductivity-type semiconductor layers with the first and second electrodes disposed on the same plane side, wherein the first electrode comprises a first pad part and a first diffusing part elongating from the first pad part as the cardinal point, facing the second electrode so that the first diffusing part is extended in the element outer circumferential direction, beyond the farthermost end part from the first pad part in the second electrode that faces therewith. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a semiconductor light emitting element, and more particularly to a semiconductor light emitting element configured by forming a pair of electrodes on the same surface side of a semiconductor light emitting element.

Conventionally, various researches and developments have been made in order to obtain a light-emitting element having excellent light distribution characteristics in a light-emitting element having a laminated structure of semiconductor layers.
For example, an n-type semiconductor layer, an active layer, and a p-type semiconductor layer are formed on the surface of the substrate, and a part of the p-type semiconductor layer and the active layer is cut away to expose the n-type semiconductor layer. In the light emitting element in which a pair of electrodes is formed on the surfaces of the n-type semiconductor layer and the p-type semiconductor layer, the reflectance on the back surface is increased by forming a reflective film on the back surface side of the substrate, There has been proposed a light-emitting element having good directivity for light extraction (for example, Patent Document 1).

  Further, as described above, in the light emitting device in which the n and p electrodes are arranged on the surface side of the substrate, for example, as shown in FIG. 9, the n electrode 2 and the p electrode 3 have pad portions 2d and 3d, respectively. And light-emitting elements 1 that are intended to diffuse a wide area without excessively concentrating current in a predetermined area (for example, , See Patent Document 2 or 3).

Further, a device in which the n-electrode is arranged so as to be surrounded by the light-emitting element, that is, the p-type semiconductor layer has been proposed (for example, Patent Documents 4 and 5).
In addition, there has been proposed a technique in which fine protrusions are provided on the outer peripheral portion of the light emitting element to improve the light emission intensity of the outer peripheral portion (for example, Patent Document 6).
JP 2005-276900 A JP 2001-345480 A JP 2000-164930 A JP 2001-308380 A JP 2005-183910 A JP 2004-221529 A

However, even if a pad portion and a diffusion portion are provided in each electrode, it is difficult to use the light emitting region widely and uniformly due to its shape, arrangement, and the like. In particular, in each electrode, even if the pad portion and / or the diffusing portion are arranged line-symmetrically or point-symmetrically with respect to the center of gravity of the light-emitting element, the current is uniformly supplied over the entire surface of the light-emitting region to uniformly emit light. That has not been realized.
When a light emitting element is incorporated in a light emitting device, the light distribution characteristics of each element greatly affects the lens design and the like, which restricts the design of the light emitting apparatus. Therefore, a light emitting element with good light distribution characteristics is desired. It is rare.

Further, in order to obtain uniform and efficient light emission characteristics, the shape and arrangement of the pad portion and the diffusion portion are studied, and even if current concentration is relaxed, if a large current is passed through such a light emitting element, As it is driven for a long time, heat is also partially generated, resulting in a new problem that the light emitting element itself may be destroyed.
Further, even if the protrusions are provided on the outer peripheral portion of the light emitting element, it has not yet been solved that the intensity becomes asymmetrical due to the shape and arrangement of each electrode, or that the peripheral light emission intensity is still extremely low.

  The present invention has been made in view of the above problems, and is uniform and efficient without inducing a region where current is concentrated on the semiconductor layer and the electrode. Even when a large current flows, both high output and high luminance are achieved. An object of the present invention is to provide a semiconductor light emitting element and a light emitting device that exhibit good light distribution characteristics while being realized.

The semiconductor light emitting device of the present invention is a semiconductor light emitting device comprising first and second electrodes on the first and second conductivity type semiconductor layers, respectively, wherein the first and second electrodes are arranged on the same surface side. ,
The second electrode includes a second pad portion disposed at one corner of the second conductive semiconductor layer, and a second pad extending annularly from the second pad portion along the outer periphery of the second conductive semiconductor layer. Consisting of a diffusion part,
The first conductive type semiconductor layer has an internal exposed region surrounded by the second conductive type semiconductor layer and an external exposed region surrounding the second conductive type semiconductor layer;
The first electrode part is formed on the internal exposed region, and the first pad part formed by displacing the center of gravity in a direction away from the center of gravity of the second pad part with respect to the center of gravity of the second conductive type semiconductor layer. And a first diffusion part extending in a direction approaching the center of gravity of the second pad part with the center of gravity of the first pad part as a base point.

In such a semiconductor light emitting device, it is preferable that a plurality of protrusions are formed in the internal exposed region and / or the external exposed region of the first conductivity type semiconductor layer. More preferably, the first electrode is disposed so as to surround the protrusion, or the protrusion in the externally exposed region is disposed so as to surround the second conductivity type semiconductor layer.
Further, the first diffusion part may extend in two directions from the first pad part.

Furthermore, another semiconductor light emitting device of the present invention includes first and second electrodes on the first and second conductivity type semiconductor layers, respectively, and the first and second electrodes are disposed on the same surface side. An element,
A first light extraction region formed inside the semiconductor light emitting device;
A second light extraction region surrounding the first light extraction region;
And a third light extraction region surrounding the second light extraction region.

In such a semiconductor light emitting element, the first light extraction region and the second light extraction region are preferably formed with a plurality of protrusions.
In addition, the first electrode is formed on a first conductive type semiconductor layer disposed inside the first light extraction region, or the second electrode is a second conductivity type that constitutes the second light extraction region. It is preferably formed on the semiconductor layer in an annular shape in the outer peripheral region.
Furthermore, in the semiconductor light emitting device described above, it is preferable that the first conductivity type semiconductor layer is an n-type nitride semiconductor layer and the second conductivity type semiconductor layer is a p-type nitride semiconductor layer.
The semiconductor light emitting device of the present invention is characterized in that the semiconductor light emitting element described above is sealed in a sealing body provided with a lens.

  According to the present invention, light distribution characteristics can be achieved while realizing both high output and high brightness even when a large current flows evenly and efficiently without causing a region where current is concentrated on the semiconductor layer and the electrode. It is possible to obtain a semiconductor light emitting device and a light emitting device excellent in the above.

(Embodiment 1)
As shown in FIG. 1 and FIGS. 2A and 2B, the semiconductor light emitting device of the present invention usually has a first conductive semiconductor layer 11, a light emitting layer 12, and a second conductive semiconductor layer 13 on a substrate 10. Are stacked in this order, and the second electrode 16 is formed on the second conductive semiconductor layer 13. The first conductivity type semiconductor layer 11 includes a second conductivity type semiconductor layer 13 and a light emitting layer 12, optionally the first conductivity type semiconductor layer 11 in the depth direction, in a partial region of one semiconductor light emitting element. The surface is exposed by removal, and the first electrode 14 is formed on the exposed surface. Therefore, the first electrode 16 and the second electrode 14 are arranged on the same surface side of the semiconductor layer.

The substrate for forming the first and second conductivity type semiconductor layers constituting the semiconductor light emitting device of the present invention is, for example, sapphire or spinel (MgA1) whose main surface is any one of the C-plane, R-plane, and A-plane. ₂ O ₄ ), an insulating substrate such as a nitride semiconductor, SiC (including 6H, 4H, 3C), ZnS, ZnO, GaAs, Si, and an oxide substrate lattice-matched with a nitride semiconductor can be used. Of these, a sapphire substrate is preferable. The insulating substrate may be finally removed or may not be removed. In addition to the first and second conductivity type semiconductor layers, a crystal nucleus forming layer, a low temperature growth buffer layer, a high temperature growth layer, a mask layer, an intermediate layer, and the like may be formed on the substrate as a base layer.

  This substrate may have a large number of irregularities on the surface. In particular, when the substrate having unevenness has a material different from that of the semiconductor layer or has a different refractive index, the interface with the first conductive type semiconductor layer on the substrate is roughened, the light distribution characteristics are excellent, and the output is high and the brightness is high. Thus, a semiconductor light emitting element and a light emitting device that realize the above can be obtained.

  Specifically, as shown in FIGS. 4A and 4B, an uneven portion 10 c is provided at the interface between the substrate 10 and the first conductivity type semiconductor layer 11. In the concavo-convex portion 10c, the planar shape of the convex portion or the concave portion may be, for example, an elliptical shape, a square / rectangular shape, a polygonal shape, or a composite shape thereof in consideration of high density arrangement and mass productivity. it can. As for the planar arrangement of the convex portions or the concave portions, it is preferable that a square / rectangular shape, a parallelogram shape, a triangular shape, a hexagonal shape (honeycomb shape) or the like is appropriately selected according to the planar shape, and is arranged at a high density. The plane size of the convex portion or the concave portion (projection portion or groove portion) is preferably larger than λ / 4n, and more preferably larger than λ / 2n. As specific dimensions in consideration of mass productivity, the width is preferably 0.5 to 5 μm, and more preferably 1 to 3 μm. Examples of the cross-sectional shape of the convex portion or the concave portion include a square / rectangular shape, a trapezoidal shape, a circular shape such as an arc / semicircle, and the like, and the size of the cross-section can be the same as the planar shape.

  Since the unevenness 10c of the substrate in FIGS. 4A and 4B is provided on the first conductivity type semiconductor layer 11 side, it faces the first electrode or the second electrode with at least the first conductivity type semiconductor layer interposed therebetween. If there are irregularities on the surface of the substrate facing the first electrode or the second electrode, conventionally, light extraction on those electrodes is reduced, and light extraction is not uniform as a whole. In particular, when the first electrode provided on the first conductivity type semiconductor layer is in the internally exposed region where the first conductivity type semiconductor layer is exposed, the decrease becomes significant. However, in the present invention, in particular, when a plurality of protrusions are formed so as to surround the first electrode in the internal exposed region of the first conductivity type semiconductor layer, it is possible to prevent a decrease in light extraction as a whole. it can. Further, when a plurality of protrusions are formed in the first light extraction region surrounded by the second light extraction region and the first electrode is disposed inside the first light extraction region, the overall light extraction is improved. Can be made.

  Furthermore, since the semiconductor light-emitting device of the present invention has the second diffusion portion in which the second electrode extends from the second pad portion along the outer periphery of the second conductivity type semiconductor layer, the entire outer periphery of the first electrode Light is extracted uniformly over the entire area, and uniform light extraction is realized as a whole.

  In the first and second conductivity type semiconductor layers, the first conductivity type usually refers to n-type or p-type, and the second conductivity type is different from the first conductivity type, that is, p-type or n-type. Show. Preferably, the first conductive semiconductor layer is an n-type semiconductor layer, and the second conductive semiconductor layer is a p-type semiconductor layer.

The first and second conductive semiconductor layers are not particularly limited, and may be any of InAlGaP-based, InP-based, AlGaAs-based, mixed crystals thereof, GaN-based nitride semiconductors, and the like. As the nitride semiconductor, a group III-V nitride semiconductor (In _x Al _y Ga _1-xy N (0 ≦ X, 0 ≦ Y, X + Y ≦ 1)) that is GaN, AlN, InN, or a mixed crystal thereof. Is mentioned. Furthermore, a mixed crystal may be used in which B is partially or entirely used as a group III element, or a part of N is substituted with P, As, or Sb as a group V element.

  Each of the first and second conductive semiconductor layers may have a single layer structure, but may have a laminated structure such as a homo structure, a hetero structure, or a double hetero structure having a MIS junction, a PIN junction, or a PN junction. .

  The first and second conductive semiconductor layers can be formed by a known technique such as metal organic chemical vapor deposition (MOCVD), hydride vapor deposition (HVPE), molecular beam epitaxy (MBE), or the like. . The thickness of the semiconductor layer is not particularly limited, and various thicknesses can be applied.

  The first and second conductivity type semiconductor layers are usually stacked with a light emitting layer interposed therebetween and doped with n-type and / or p-type impurities to indicate either the first conductivity type or the second conductivity type. In the case of a stacked structure, a layer not doped with impurities may exist on the side of each layer on which the first and second conductivity type semiconductor layers are formed with the light emitting layer interposed therebetween, or both or either of them. However, there may be a layer that does not exhibit any conductivity type, a layer that exhibits the opposite conductivity type, or the like.

  The first conductive type semiconductor layer suitably contains an impurity and has a layer structure that realizes supply and diffusion of carriers to the electrode formation surface and the light emitting layer. In particular, in order to supply carriers by in-plane diffusion from the electrode toward the light emitting layer, it is preferable to have a contact layer that is relatively highly doped. Furthermore, it is preferable to have an intervening layer that moves and supplies charges to the light emitting layer in the stacking direction, a cladding layer that confines the first conductivity type carrier to the light emitting layer, and the like. The layer provided between the light emitting layer and the contact layer is preferably provided with a relatively lightly doped amount or an undoped layer and / or a multilayer film layer. Thereby, the crystallinity of the clad layer and / or the light emitting layer grown thereon can be improved, the in-plane diffusion of current can be promoted during driving, and the pressure resistance can be improved. The multilayer film layer is preferably formed with a periodic structure or a superlattice structure in which at least two kinds of layers are alternately laminated.

  As the light emitting layer, in particular, a nitride semiconductor in which a nitride semiconductor containing In is used for the light emitting layer is preferable because a suitable light emitting efficiency is obtained in the ultraviolet to visible light (red light) region. Further, a quantum well structure such as a single quantum well structure or a multiple quantum well structure is preferable.

  The second conductivity type semiconductor layer may include a clad layer that confines carriers in the light emitting layer, a contact layer on which an electrode is formed, and the like. The nitride semiconductor is preferably a nitride semiconductor containing Al as a cladding layer. Further, a layer having a lower impurity concentration than those layers may be interposed between the contact layer and the cladding layer. Thereby, an element with a high electrostatic withstand voltage can be formed, and the crystallinity can be improved even if the contact layer is doped at a high concentration.

  Specifically, for example, as shown in FIG. 6, a GaN buffer layer 10 a and a non-doped GaN layer 10 b are stacked on a sapphire substrate 10, and a Si-doped GaN serving as a contact layer 11 a as a first conductivity type semiconductor layer 11. Si-doped GaN layer serving as the n-type cladding layer 11b; InGaN layer serving as the light emitting layer 12; Mg-doped AlGaN layer serving as the p-type cladding layer 13a serving as the second conductive semiconductor layer 13, and Mg-doped GaN serving as the contact layer 13b The layers have a layer structure in which the layers are sequentially stacked.

  As described above, the first conductivity type semiconductor layer is exposed by removing the second conductivity type semiconductor layer and the light emitting layer, and optionally a part of the first conductivity type semiconductor layer in the depth direction. For example, as shown in FIG. 1, the conductive semiconductor layer has an internal exposed region 11 bb surrounded by the second conductive semiconductor layer 13 and an external exposed region 11 aa surrounding the second conductive semiconductor layer 13. Yes. That is, the light emitting layer does not exist in the internal exposure area and the external exposure area.

  The internal exposure region is preferably composed of a first pedestal region and a first extension region. The first pedestal region is arranged with the center of gravity displaced in a direction away from the center of gravity of the second pad portion of the second electrode, which will be described later, with respect to the center of gravity of the second conductive semiconductor layer 13 (based on the center of gravity). (Refer to 11x in FIG. 1, 21x in FIG. 5 (a), and 31x in FIG. 5 (b)). In other words, when the light emitting element is divided into a second pad portion side to be described later and the opposite side thereof by a line passing through the center of gravity of the light emitting element, the first pedestal region is arranged biased to the opposite side. .

  Note that the internal exposure region functions as one of the light extraction regions. That is, since the light emitting layer is not formed, the region itself does not emit light, but when the light emitting layer emits light, a part of the light in the lateral direction gathers in the internal exposed region and exists in the internal exposed region. The light can be extracted from the light extraction surface, for example, the surface on the side where the second conductivity type semiconductor layer is formed, by being reflected by the first conductivity type semiconductor layer.

  The first extension region preferably extends from the center of gravity of the first pedestal region in a direction approaching the center of gravity of the second pad portion. Here, the direction of approaching the center of gravity of the second pad portion is not only from the direction of approaching the center of gravity at the shortest distance of the second pad portion from the first pedestal region, but also from the base point in the first pedestal region of the first extension region, Any direction that shortens the distance to the center of gravity of the second pad portion may be used (see FIGS. 1, 5A, and 5B). The first extension region may extend from the first pedestal region in one direction, linearly or in a curved shape (see FIG. 5B), or may extend in a plurality of directions, for example, two directions. (See FIG. 1 and FIG. 5 (a)). In the latter case, the first extension regions extending in each direction preferably have the same length (FIG. 1), but may be different (FIG. 5 (a)). From another point of view, it is preferable that the internal exposure region composed of the first pedestal region and the first extension region is not arranged point-symmetrically. Furthermore, although it may be arrange | positioned symmetrically with respect to one symmetry line, it is more preferable that it is not arrange | positioned symmetrically with respect to two or more symmetry lines. From another viewpoint, it is preferable that there is at least one straight line that is symmetrical with respect to the light emitting element with respect to an arbitrary straight line that passes through the light emitting element (see, for example, FIG. 1). Thereby, better alignment characteristics can be obtained.

  The internal exposed region is not limited to the planar shape as described above, but may have any shape, but may have a shape corresponding to the shape of the first electrode, which will be described later, or a shape that is substantially similar to the first electrode. preferable. Thereby, the light emitting area can be secured to the maximum.

  The external exposure area functions as one of the light extraction areas. That is, like the internal exposure region, since the light emitting layer is not formed, the region itself does not emit light, but when the light emitting layer emits light, a part of the lateral light gathers in the external exposure region. The light can be extracted from the light extraction surface, for example, by being reflected by the first conductive semiconductor layer present in the externally exposed region.

  The first electrode is formed inside the semiconductor light emitting element, in other words, on the internally exposed region. In other words, the first electrode is not disposed at the element end, but is disposed so that the entire outer periphery thereof is surrounded by the second conductivity type semiconductor layer. Thereby, the spread of the electric current in the surface direction from the second electrode can be more efficiently extracted from the entire periphery of the first electrode.

  The first electrode is formed by the first pad portion and the first diffusion portion. The first pad portion is arranged with the center of gravity displaced in a direction away from the center of gravity of the second pad portion with respect to the center of gravity of the second conductive type semiconductor layer. The first diffusing portion is disposed so as to extend in a direction approaching the centroid of the second pad portion with the centroid of the first pad portion as a base point. From another viewpoint, the first electrode is formed including a first pad portion and a first diffusion portion extending from the first pad portion as a base point from the first pedestal region of the internal exposure region to the first extension region. Yes. By adopting such a shape, the current easily spreads evenly, and partial heat generation can be avoided.

It is preferable that the 1st pad part is arrange | positioned corresponding to the shape in the 1st base area | region mentioned above. The magnitude | size of a 1st pad part is not specifically limited, It can adjust suitably with the size of a semiconductor light-emitting device, etc. For example, it is exemplified that the semiconductor light emitting element is formed with an occupied area of about 7 to 10%. Specifically, about 9000-14000 micrometers ² is mentioned.

  The first diffusion part may extend from the first pad part only in one direction, linearly or in a curved line, or may extend in a plurality of directions, for example, two directions. Moreover, it is preferable that the 1st spreading | diffusion part is extended toward the 2nd pad part mentioned later. Thereby, since the space | interval with a 2nd electrode can be shortened, the flow of an electric current can be adjusted within a light emission surface. That is, it is preferable that the 1st spreading | diffusion part is arrange | positioned corresponding to the shape in the 1st extension area | region. Furthermore, the first diffusion portion may be formed with a uniform width in all of them, and when formed partially or in a plurality of directions, the width may be different for each direction. In particular, when the first diffusion portion extending in a plurality of directions is formed, the width may be varied depending on the length. Thereby, the current flowing through the first diffusion portion can be made uniform regardless of the length of the first diffusion portion. In addition, the width | variety of a 1st diffused part can be suitably adjusted with the length, the size of a semiconductor light-emitting device, etc. For example, the area of all the 1st diffused parts is 0.5-1.5 of a semiconductor light-emitting device. It is illustrated that it is formed with an occupied area of about%. From another viewpoint, the width is set to about 5 to 15% of the width (maximum length) of the first pad portion. Specifically, about 5-15 micrometers is mentioned.

  The second electrode includes a second pad portion disposed at one corner of the second conductivity type semiconductor layer, and a second diffusion portion extending from the second pad portion along the outer periphery of the second conductivity type semiconductor layer. . In this case, the outer periphery is preferably the entire outer periphery. With such a configuration, a current can be supplied uniformly over the entire surface of the second conductivity type semiconductor layer.

The second pad portion is preferably formed at one corner, but may be formed at two or more corners. The size of the second pad portion is not particularly limited and can be appropriately adjusted depending on the size of the semiconductor light emitting element. For example, it is exemplified that the semiconductor light emitting element is formed with an occupied area of about 7 to 15%. From another viewpoint, it is exemplified that the first pad portion is formed with a size of about 50 to 200%. A specific example is about 5000~25000μm ^2.

  The second diffusion portion is preferably formed with a uniform width in all of the second diffusion portions, but the width may be partially different. The width of the second diffusion portion can be adjusted as appropriate depending on the size of the semiconductor light emitting element, and for example, the area of all the second diffusion portions is formed with an occupied area of about 5 to 15% of the semiconductor light emitting element. Is exemplified. From another viewpoint, setting the width to about 5 to 15% of the width (maximum length) of the second pad portion is exemplified. Further, from another viewpoint, it is exemplified that the first diffusion portion is formed with a width of about 50 to 200%. Specifically, about 5 to 15 μm can be mentioned.

  The second electrode is preferably electrically connected to the second conductivity type semiconductor layer via a translucent electrode formed on substantially the entire surface of the second conductivity type semiconductor layer. Thereby, current can be more efficiently supplied to the entire surface of the second conductivity type semiconductor layer, and uniform light emission can be obtained.

The first and second electrodes, optionally translucent electrodes, for example, nickel (Ni), platinum (Pt) palladium (Pd), rhodium (Rh), ruthenium (Ru), osmium (Os), iridium (Ir) , Titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), cobalt (Co), iron (Fe), manganese (Mn), molybdenum (Mo) Transparent such as chromium (Cr), tungsten (W), lanthanum (La), copper (Cu), silver (Ag), yttrium (Y), oxides or nitrides thereof, ITO, ZnO, In ₂ O ₃ It can be formed of a single layer film or a laminated film of a metal or alloy containing at least one selected from the group consisting of conductive oxides. The film thickness is not particularly limited and can be appropriately adjusted in consideration of the characteristics to be obtained. In addition, the pad part and diffusion part which comprise an electrode do not necessarily need to be integrally formed simultaneously with the same material, and may have a different material and / or film thickness. Moreover, it is preferable that the pad part usually has a film thickness and an area necessary for effectively functioning for connection with an external electrode.

  Note that the region where the second conductivity type semiconductor layer is disposed functions as one of the light extraction regions. That is, since the light emitting layer is formed under the light emitting layer, when the light emitting layer emits light, light is emitted to the second conductive semiconductor layer side, and light can be extracted from the light extraction surface.

(Embodiment 2)
As shown in FIG. 3, the semiconductor light emitting device of the present invention has a substantially entire surface or a partial region in one or both of the internal exposed region 11 b and the external exposed region 11 a of the first conductivity type semiconductor layer 11. A plurality of protrusions 29 are formed.
In particular, it is preferable that the protrusion in the internal exposure region is disposed so as to surround the first electrode, and the protrusion in the external exposure region is disposed so as to surround the second conductivity type semiconductor layer. Is preferred. Thereby, the light radiate | emitted from the end surface of a semiconductor laminated structure can be taken out to an upper surface efficiently.

  The projection may have any shape such as a quadrangle, trapezoid, or semicircle, but the trapezoid, that is, the truncated cone shape in which the projection 29 itself gradually narrows as shown in FIG. It is preferable that In this case, the inclination angle of the protrusion may be, for example, 30 ° to 80 °, and preferably 40 ° to 70 °. In other words, the light that has been light-reflected from the light emitting layer by totally reflecting the light from the light emitting layer or being guided through the first conductive semiconductor layer 11 by being inclined so that the protrusion gradually becomes thinner toward the tip. As a result, light extraction toward the second conductivity type semiconductor layer 13 can be effectively performed. In addition, the directivity control of light becomes easier and more uniform light extraction is possible as a whole.

  When the protrusion has a truncated cone shape, a recess may be further formed on the upper side of the trapezoid (on the first semiconductor layer side). Thereby, when the light guided in the second semiconductor layer enters the inside of the protrusion, light is easily emitted to the first semiconductor layer side by the concave portion formed at the top of the protrusion.

  It is preferable that the protrusions are arranged to be at least partially overlapped by 2 or more, preferably 3 or more, in a direction substantially perpendicular to the emission end face of the semiconductor layer. Thereby, since the light from a light emitting layer can be made to act on a protrusion with high probability, the said effect can be acquired more easily.

The density of the protrusions is not particularly limited, and may be at least 100, preferably 200, more preferably 300, more preferably 500 or more in one semiconductor light emitting device. Thereby, the said effect can be improved more. Note that, as viewed from the electrode forming surface side, the ratio of the area occupied by the protruding portion in the exposed region of the first conductivity type semiconductor layer is 20% or more, preferably 30% or more, more preferably 40% or more. It can be. The upper limit is not particularly limited, but is preferably 80% or less. In addition, the area of one protrusion is 3 to 300 μm ² , preferably 6 to 80 μm ² , and more preferably 12 to 50 μm ² at the root of the protrusion.

  Thus, by forming the protrusion, (1) the light guided in the first conductivity type semiconductor layer is taken into the protrusion, and is extracted from the top of the protrusion or the middle part thereof, (2) Light guided in the first conductivity type semiconductor layer is irregularly reflected and extracted at the base of the protrusion, and (3) Light emitted from the end surface of the light emitting layer to the side is reflected by the plurality of protrusions. It is considered that the light is scattered and extracted, that is, the light emitted in the lateral direction (side surface direction of the semiconductor light emitting element) can be selectively emitted to the second conductive type semiconductor layer side by the unevenness, and thereby the light extraction The efficiency can be improved by, for example, about 10 to 20%, and the light directivity can be controlled. In particular, in a semiconductor light emitting device having a structure in which a light emitting layer is sandwiched between layers having a lower refractive index (so-called double heterostructure), light is confined between the layers having a lower refractive index, so This is particularly effective for a light emitting element having such a structure. Furthermore, by providing a plurality of projections and depressions, uniform light extraction can be achieved over the entire region on the second conductivity type semiconductor layer side.

  The protrusion may be subjected to a special process for forming the protrusion, for example, by growing a semiconductor layer on the exposed first conductive type semiconductor layer. However, the first conductive type semiconductor layer is exposed. At the time, or when a predetermined region is thinned to divide into each chip, it is preferable to form simultaneously using this process. Thereby, the increase in a manufacturing process can be suppressed. Thus, since the protrusion is composed of the same stacked structure as the semiconductor stacked structure of the semiconductor light emitting element, that is, a plurality of layers made of different materials, the light taken into the protrusion due to the difference in the refractive index of each layer. However, it becomes easy to reflect in the interface of each layer, and as a result, it is thought that it can contribute to the light extraction improvement to the 2nd conductivity type semiconductor layer side.

  As shown in FIG. 6, the protrusion is required to be higher than at least the interface between the light emitting layer 12 and the second conductive semiconductor layer 11 adjacent thereto in the cross section of the semiconductor light emitting device, but the first conductive type is higher than the light emitting layer 12. The top is preferably located on the semiconductor layer 13 side, and more preferably substantially the same height as the first conductivity type semiconductor layer 13. That is, it is preferable that the top of the protrusion 29 is formed to be higher than the light emitting layer 12. By configuring the protrusions so as to include the second conductivity type semiconductor layer, the tops thereof have substantially the same height, so that the second conductive layer is not interrupted by the first electrode, which will be described later. Light can be effectively extracted to the mold semiconductor layer side. By configuring the protrusion to be higher than the second conductivity type semiconductor layer, preferably the second electrode, light can be extracted more effectively. Moreover, the recessed part between protrusions should just be lower than the interface of a light emitting layer and the 2nd conductivity type semiconductor layer adjacent to it at least, and it is preferable that it is formed so that it may become lower than a light emitting layer.

(Experimental example 1)
On the substrate 10 made of sapphire, a buffer layer (not shown) made of Al _0.1 Ga _0.9 N and a non-doped GaN layer (not shown) are stacked, and a Si layer 11 is formed as a first conductivity type semiconductor layer 11 thereon. An n-type contact layer made of doped GaN, a superlattice n-type clad layer in which a GaN layer (40Å) and an InGaN layer (20Å) are alternately laminated 10 times are laminated, and further, a GaN layer (250Å) As the second conductivity type semiconductor layer 13, the Mg-doped Al _0.1 Ga _0.9 N layer (40Å) and the Mg-doped InGaN are used as the light emitting layer 12 having a multiple quantum well structure in which 3 and 6 layers of InGaN and InGaN layers (30Å) are alternately stacked three to six times. As shown in FIG. 1, the superlattice p-type clad layer and the p-type contact layer made of Mg-doped GaN are laminated in this order. Body light emitting element (450 [mu] m □, blue) to form.

In this semiconductor light emitting device, the first conductivity type semiconductor layer 11 includes a second conductivity type semiconductor layer 13, a light emitting layer 12, and a part of the first conductivity type semiconductor layer 11 removed in the depth direction. An internal exposed region 11bb surrounded by the semiconductor layer 13 and an external exposed region 11aa surrounding the second conductivity type semiconductor layer 13 are provided.
The internal exposure region 11bb is composed of a first pedestal region 11x and a first extension region 11y.

The first pedestal region 11x is arranged with the center of gravity displaced in a direction away from the center of gravity of the second pad portion 16a of the second electrode, which will be described later, with the center of gravity of the second conductive semiconductor layer 13 as a reference.
The first extension region 11y extends from the center of gravity of the first base region 11x in two directions approaching the center of gravity of the second pad portion 16a.

  On the internal exposure region 11bb, a first pad portion 14a and two first diffusion portions 14b extending from the first pad portion 14a are provided corresponding to the first pedestal region 11x and the first extension region 11y, respectively. The first electrode 14 (Rh / Pt / Au: 7000 mm) is formed.

The size of the first pad portion 14a is, for example, an occupied area of about 8% of the semiconductor light emitting element, that is, about 12000 μm ² .
The first diffusion portion 14b is formed with a width of about 10% of the maximum width of the first pad portion 14a, specifically, a width of about 10 μm, for example.

The second electrode includes a second pad portion 16a disposed at one corner of the second conductivity type semiconductor layer, and a second diffusion portion extending from the second pad portion 16a along the outer periphery of the second conductivity type semiconductor layer 13. 16b.
The second pad portion 16a is formed with an occupied area of about 15% of the semiconductor light emitting element, for example. Specifically, it is about 23000 μm ² .
For example, the second diffusion portion is set to a width of about 10% of the maximum width of the second pad portion 16a, and specifically, has a width of about 10 μm.

  The second electrode 16 is electrically connected to the second conductive semiconductor layer 13 via a transparent electrode 15 (5000 mm) made of ITO formed on the second conductive semiconductor layer 13 on almost the entire surface. ing. As for the 2nd electrode 16, W layer, Pt layer, and Au layer (total film thickness of 1 micrometer) are laminated | stacked in this order.

About such a semiconductor light-emitting device, the light distribution characteristic was measured with the following measurement environments.
Measuring instrument: STM light distribution measuring instrument Driving mode: Pulse driving (pulse width = 500 μs, pulse period = 1 ms, exposure time = 19 ms, gain = 2 times)
Application condition: 100 mA

  For comparison, as shown in FIGS. 7A and 7B, the planar shapes of the first electrodes 44 and 54 (n electrode) and the second electrodes 46 and 56 (p electrode) and the corresponding shapes are shown. The same light emitting element is formed except that the first conductive semiconductor layer (particularly the internal exposed region) and the second conductive semiconductor layer have different planar shapes (not shown), and the light distribution is similarly performed in the same measurement environment. Characteristics were measured. The result is shown in FIG. Note that the measurement results corresponding to FIGS. 7A and 7B are shown as Comparative Example A and Comparative Example B, respectively. Each light emitting element was n = 3.

  From the results of FIG. 8, the light emitting element of the present invention has φ = 0 ° (in FIG. 1, the axis in the X direction passing through the center of gravity of the light emitting element) and 90 ° (in FIG. 1, in the Y direction passing through the center of gravity of the light emitting element). In any direction of the axis), it was confirmed to be flat and exhibit very good light distribution characteristics. On the other hand, in both Comparative Example A and Comparative Example B, the light emission intensity is small in the central portion of the light emitting element in both directions of φ = 0 ° and 90 °, and the light distribution characteristic having a double peak is obtained. Stayed to show.

(Experimental example 2)
As shown in FIG. 3, the semiconductor element of this experimental example is the same as that of Experimental Example 1 except that a plurality of protrusions 29 are formed in the inner exposed region 11bb and the outer exposed region 11aa of the first conductivity type semiconductor layer. The configuration is substantially the same as that of the light emitting element.
The size of the protrusion 29 is about 20 μm ² near the base thereof, the total number of the protrusions is about 1000, and the area occupied by the protrusions in one light emitting element is about 15%.
By forming such protrusions, it was confirmed that the light emission intensity itself was improved by about 10% while being flat and exhibiting very good light distribution characteristics as in Experimental Example 1.

(Experimental example 3)
As shown in FIGS. 4A and 4B, the semiconductor element of this experimental example has substantially the same configuration as the light-emitting element of Experimental example 1 except that the uneven portion 10c is provided on the surface of the substrate 10. is there.
The uneven portion 10c has, for example, a height of 0.8 μm, a planar shape close to a circle, a dot shape, and a cross-sectional shape that is close to a trapezoid (a shape in which opposite sides that are not parallel are curved outwards) ). The convex part has a diameter of the lower part of the convex part of 2 μm, and an interval between the convex part and the adjacent convex part (shortest distance of the concave part) is 1 μm.
It was confirmed that by forming such an uneven portion 10c, the light emission intensity itself was improved by about 10%, and the flat and very good light distribution characteristics were exhibited as in Experimental Example 1.

(Experimental example 4)
As comparative examples, the shapes of various conventionally known first conductive semiconductor layers, second conductive semiconductor layers, and electrodes (n: n electrode, p: p electrode) shown in FIGS. In the same manner as described above, the light distribution characteristics were confirmed in the same manner as described above. In FIGS. 10A to 10C, the light emission intensity at the central portion of the light emitting element was the same as in Comparative Examples A and B described above. Is small and only shows the light distribution characteristic having a double peak. Further, in FIGS. 10B to 10F, only the left-right asymmetric alignment characteristics were obtained due to the positional deviation of each electrode. Furthermore, in all of FIGS. 10A to 10F, the emission intensity at the outer peripheral portion was extremely small.

  The present invention can be used for an illumination light source, an LED display, a backlight light source such as a mobile phone, a traffic light, an illumination switch, an in-vehicle stop lamp, various sensors, and various indicators.

It is a schematic plan view for demonstrating the structure of the semiconductor light-emitting device of this invention. FIG. 2 is a schematic cross-sectional view taken along line (a) A-A ′ and (b) B-B ′ of the semiconductor light emitting device of FIG. 1. It is a schematic plan view for demonstrating another structure of the semiconductor light-emitting device of this invention. It is a (a) A-A 'and (b) B-B' line schematic sectional drawing for demonstrating another structure of the semiconductor light-emitting device of this invention. It is a schematic plan view for demonstrating another structure of the semiconductor light-emitting device of this invention. FIG. 4 is a schematic sectional view taken along line B-B ′ of the semiconductor light emitting device of FIG. 3. It is a schematic plan view showing the structure of a semiconductor light emitting device for comparison. It is a graph which shows the light distribution characteristic of the semiconductor light-emitting device of this invention. It is a schematic plan view for demonstrating the structure of the conventional semiconductor light-emitting device. It is a schematic plan view for demonstrating another structure of the conventional semiconductor light-emitting device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Substrate 10a GaN buffer layer 10b Undoped GaN layer 10c Uneven portion 11 Second conductive semiconductor layer 11a n-type contact layer 11b n-type cladding layer 11aa Externally exposed regions 11bb, 21b, 31b Internally exposed regions 11x, 21x, 31x First base Region 11y, 21y, 31y First extension region 12 Light emitting layer 13 First conductive semiconductor layer 13a P-type cladding layer 13b P-type contact layers 14, 24, 34 First electrodes 14a, 24a, 34a First pad portions 14b, 24b 34b First diffusion part 15 Translucent electrode 16 Second electrode 16a Second pad part 16b Second diffusion part 29 Projection

Claims (10)

A semiconductor light emitting device comprising first and second electrodes on the first and second conductivity type semiconductor layers, respectively, wherein the first and second electrodes are disposed on the same plane side,
The second electrode includes a second pad portion disposed at one corner of the second conductive semiconductor layer, and a second pad extending annularly from the second pad portion along the outer periphery of the second conductive semiconductor layer. Consisting of a diffusion part,
The first conductive type semiconductor layer has an internal exposed region surrounded by the second conductive type semiconductor layer and an external exposed region surrounding the second conductive type semiconductor layer;
The first electrode part is formed on the internal exposed region, and the first pad part formed by displacing the center of gravity in a direction away from the center of gravity of the second pad part with respect to the center of gravity of the second conductive type semiconductor layer. And a first diffusion portion extending in a direction approaching the center of gravity of the second pad portion with the center of gravity of the first pad portion as a base point.   2. The semiconductor light emitting device according to claim 1, wherein a plurality of protrusions are formed in an internal exposed region and / or an external exposed region of the first conductivity type semiconductor layer.   The semiconductor light emitting element according to claim 2, wherein the protrusion in the internal exposure region is disposed so as to surround the first electrode.   4. The semiconductor light emitting element according to claim 2, wherein the protrusion in the externally exposed region is disposed so as to surround the second conductivity type semiconductor layer.   The semiconductor light emitting element according to claim 1, wherein the first diffusion portion extends in two directions from the first pad portion. A semiconductor light emitting device comprising first and second electrodes on the first and second conductivity type semiconductor layers, respectively, wherein the first and second electrodes are disposed on the same plane side,
A first light extraction region formed inside the semiconductor light emitting device;
A second light extraction region surrounding the first light extraction region;
A third light extraction region surrounding the second light extraction region, and the first electrode is formed on a first conductivity type semiconductor layer disposed inside the first light extraction region. A semiconductor light emitting element characterized by the above.   The semiconductor light emitting element according to claim 6, wherein the first light extraction region and the third light extraction region are formed with a plurality of protrusions.   8. The semiconductor light emitting device according to claim 6, wherein the second electrode is formed on the second conductivity type semiconductor layer constituting the second light extraction region, and is formed in an annular shape in the outer peripheral region thereof. 9. element.   The semiconductor light-emitting element according to claim 1, wherein the first conductivity type semiconductor layer is an n-type nitride semiconductor layer, and the second conductivity type semiconductor layer is a p-type nitride semiconductor layer. A semiconductor light-emitting device, wherein the semiconductor light-emitting element according to claim 1 is sealed in a sealing body including a lens.

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