JP4404097B2 - Semiconductor light emitting device - Google Patents

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 research and development have been conducted in order to realize a large area in a light-emitting element having a laminated structure of semiconductor layers.
For example, in the element 1 in which a nitride semiconductor layer is stacked on an insulating substrate such as a sapphire substrate, the p-type semiconductor layer 4 and a part of the active layer are removed to a depth as shown in FIG. The type semiconductor layer 5 is exposed, and a pair of electrodes of an n-electrode 2 and a p-electrode 3 are provided on the surfaces of these semiconductor layers, that is, on the same surface side of the nitride semiconductor layer. These n electrode 2 and p electrode 3 are each composed of pedestal portions 2d and 3d and extending portions 2e and 3e extended therefrom, and the current is not excessively concentrated in a predetermined region and is wide. It is intended to diffuse into the region (for example, see Patent Documents 1 to 5).
JP 2001-345480 A JP 2000-164930 A JP 2004-56109 A JP 2002-319705 A JP 2005-19646 A

  However, even if a pedestal portion and an extension 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 addition, when each electrode is enlarged or deformed in order to widely use the light emitting region, a region where current is excessively concentrated may appear, and uniform and efficient light emitting characteristics cannot be obtained.

In order to obtain uniform and efficient light emission characteristics, the shape and arrangement of the pedestal part and the extension part are studied, and even if current concentration is relaxed, if a large current is passed through such a light emitting element, As it was driven, heat was also partially generated, leading to a new problem that the light emitting element itself could be destroyed.
In particular, when the light-emitting element is formed of a nitride semiconductor layer, the n-type semiconductor layer and the p-type semiconductor layer have different specific resistances. Therefore, in the p-electrode electrically connected to the p-type semiconductor layer having a high resistance. , There was a tendency to be partially destroyed.

  The present invention has been made in view of the above problems, and it is uniform without causing a region where current is concentrated on the semiconductor layer and the electrode regardless of the composition, film thickness, shape, conductivity type, resistance value, and the like of the semiconductor layer. An object of the present invention is to provide a semiconductor light emitting device that is efficient and has a long life while avoiding the destruction of the semiconductor layer and the electrode while realizing both high output and high luminance even when a large current flows.

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 first electrode includes a first pedestal portion and at least two first extending portions extending in the same direction from the first pedestal portion, and the second electrode includes a second pedestal portion and the second pedestal portion. A second extending portion extending in substantially the same direction as the first extending portion so as to approach the first pedestal portion from the pedestal portion;
Each of the at least two first extending portions has a terminal portion disposed in the outer peripheral direction of the second electrode beyond the end portion farthest from the first pedestal portion in the same direction portion, The first extending part is provided with the first pedestal part in the same direction part, and the other first extending part is arranged so that the distance between the first electrode and the second electrode is the shortest in the same direction part,
The second extending portion includes a shortest distance between the same direction portion of the other first extending portion and the second pedestal portion, and the same direction portion of the other first extending portion and the second extending portion. It is characterized by being extended from the second pedestal so that the shortest interval is the same.

In such a semiconductor light emitting device, two or more of the second electrodes are formed,
The first electrode has three first extending portions,
The three first extending portions have one first extending portion in which only one first pedestal portion is provided in the same direction portion, and the distance between the first electrode and the second electrode is the shortest in the same direction portion. Two other first extending portions arranged so as to be, or one first extending portion arranged so that the distance between the first electrode and the second electrode is the shortest in the same direction portion, It is preferable that the two first extending portions are provided with one first pedestal portion in the same direction portion.

  The distance between the second pedestal portion and the first pedestal portion is preferably equal to or greater than the distance between the second pedestal portion and the outer periphery of the element.

Furthermore, a light emitting layer is provided between the second conductive type semiconductor layer and the first conductive type semiconductor layer, and the second conductive type semiconductor layer includes the first conductive type semiconductor layer and a part of the region. The light emitting layer is removed and its surface is exposed,
Preferably, the second electrode is provided on the exposed surface, and an outer periphery thereof is surrounded by the first conductive semiconductor layer.

  According to the present invention, regardless of the composition, film thickness, shape, conductivity type, resistance value, etc. of the semiconductor layer, even when a current is applied to the semiconductor layer, a region where current is concentrated on the semiconductor layer and the electrode is caused. And uniform and efficient light emission. In addition, even when a large current is passed, it is possible to obtain a semiconductor light emitting element with a long life while avoiding the destruction of the semiconductor layer and the electrode while realizing both high output and high luminance.

Embodiments of a semiconductor light emitting device according to the present invention will be described below in detail with reference to the drawings.
(Embodiment 1)
As shown in FIG. 1, the semiconductor light emitting device of the present invention usually has a second conductive semiconductor layer 11, a light emitting layer 12, and a first conductive semiconductor layer 13 stacked in this order on a substrate. A first electrode 16 is formed on the conductive semiconductor layer 13. In this semiconductor light emitting device, the second conductivity type semiconductor layer 11 includes the first conductivity type semiconductor layer 13 and the light emitting layer 12, and optionally the second conductivity type semiconductor layer 11 in a partial region of one semiconductor light emitting device. Part of the depth direction is removed to expose the surface, and the second 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. Further, as shown in FIG. 2, the first electrode 16 is disposed so as to face the second electrode 14, in other words, so as to surround a part of the second electrode 14.

  The first electrode is composed of a first pedestal portion and at least one, preferably two or more first extending portions extending from the first pedestal portion. For example, as shown in FIG. 2, the first electrode 16 includes a first pedestal portion 16a and a first extending portion 16b, and may further include another first extending portion 16c. With such a configuration, a current can be supplied uniformly over the entire surface of the first conductivity type semiconductor layer. In addition, the number of the 1st base part may be one, and two or more may be formed. In connection with this, a 1st extending | stretching part is also formed as mentioned above corresponding to each 1st base part. It is preferable. The first extending portion 16b is connected to the second electrode 14, in particular, the second electrode facing the first electrode 16 including the first extending portion 16b, in other words, the first pedestal portion 16a from which the first extending portion 16b extends. It extends in the element outer peripheral direction beyond the end portion 14aa farthest from the first pedestal portion 16a in the nearest second electrode. This means that the distance between the first extending portion 16b and the outer peripheral edge portion of the second electrode 14 is the distance between the end portion 14aa of the second electrode and the outer peripheral portion of the element. Means shorter than distance. Thereby, destruction of the first electrode in the shortest region between the first and second electrodes can be effectively prevented.

  As shown in FIG. 2, when the first electrode 16 includes two or more first extending portions, the widths of all the first extending portions may be the same, but the width of one first extending portion 16b. (W1 in FIG. 1) is preferably different from the width (w2 in FIG. 1) of the other first extending portion 16c. With such a configuration, the width can be changed according to the distance of the first extending portion from the first pedestal portion, and the current injected or extracted from the first pedestal electrode can be adjusted. In particular, it is preferable that the first extending portion 16b including the end portion 16bb farther from the first pedestal portion 16a is wider than the first extending portion 16c including the end portion 16cc closer to the first pedestal portion 16a. Thereby, the electric current which flows into a 1st extending | stretching part can be made uniform irrespective of the length of a 1st extending | stretching part.

For example, the width (w1) of the first extending portion 16b is suitably about 1 to 100%, particularly about 10 to 50% wider than the width (w2) of the first extending portion 16c. Specifically, the width (w1) of the first extending portion 16b is about 10 to 60 μm, and the width (w2) of the first extending portion 16c is about 5 to 55 μm.
The first electrode 16 may be electrically connected to the first conductive type semiconductor layer 13 through a translucent third electrode 15 formed on almost the entire surface of the first conductive type semiconductor layer 13. . Thereby, current can be more efficiently supplied to the entire surface of the first conductive semiconductor layer 13 and uniform light emission can be obtained.

  For example, as shown in FIGS. 1 and 2, the second electrode 14 is preferably arranged inside the semiconductor light emitting element, in other words, the outer periphery thereof is surrounded by the first conductivity type semiconductor layer 13. That is, it is preferable that the second electrode is disposed not inside the element end but inside the element. Thereby, the spread of the current from the first electrode in the surface direction can be more efficiently extracted from the entire periphery of the second electrode. In addition, it is preferable that the distance between the second pedestal portion and the first pedestal portion is equal to or greater than the distance between the second pedestal portion and the outer periphery of the element. As a result, current can be injected or extracted efficiently even at the outer periphery of the element, and current concentration can be reduced. In addition, it is preferable that two or more second electrodes 14 are formed from the viewpoint of more efficiently performing current extraction and enabling a large area of the element. In this case, it is preferable that the outer periphery of each second electrode 14 is disposed so as to be surrounded by the first conductivity type semiconductor layer 13.

  Moreover, it is preferable that the 2nd electrode 14 is equipped with the 2nd base part 14a and the 2nd extending | stretching part 14b extended on the basis of this 2nd base part 14a. In particular, the second extending portion 14b is preferably extended in the same direction as the first extending portions 16b and 16c. With such a configuration, current easily spreads evenly in a region where the second extending portion 14b and the first extending portion 16b face each other, and it is possible to avoid the destruction of electrodes and elements due to heat in that region. It is preferable that the 2nd extending | stretching part 14b is normally extended | stretched so that the 1st pedestal part 16a of the 1st electrode which opposes may approach from the 2nd pedestal part 14a normally.

  The second extending portion 14b is the shortest interval between the second pedestal portion 14a and the first extending portion 16b (x1 in FIG. 1) and the shortest interval between the second extending portion 14b and the first extending portion 16b (in FIG. 1, x2 and x3) preferably extend from the end of the second pedestal portion 14a (particularly in the same direction as the extending direction of the first extending portion 16b as described above) so that x2 and x3) are the same. Since the distance between the first extending portion 16b of the first electrode 16 and the second extending portion 14b of the second electrode 14 can be reduced, the current flow can be adjusted within the light emitting surface, and the first The shortest distance between the extending portion 16b and the second extending portion 14b can be secured in a certain wide area.

  The first electrode 16 and the second electrode 14 are usually arranged so that the distance between them is different at each part, for example, as indicated by x1 to x6 in FIG. In FIG. 2, x1 to x3 are the same, but x4 to x6 are different from x1 to x3, respectively. In this semiconductor light emitting device, the first extending portion 16b including the terminal end portion 16bb farther from the first pedestal portion 16a in the second extending portion 14b of the second electrode 14 in the interval from the first electrode 16 to the second electrode 14. It is preferable that they are arranged with the shortest interval with respect to (refer to the region from x1 to x3). By setting it as such a structure, the space | interval of the 1st extending | stretching part 16b and the 2nd extending | stretching part 14b which are more distant from the 1st base electrode 16a can be shortened, and an electric current flow is adjusted within a light emission surface. be able to. In addition, a region where light emission is darker than other regions can be eliminated, and uniform light emission can be obtained.

In the positional relationship between the first electrode 16 and the second electrode 14, the first extending portion 16b and the second extending portion 14b have the shortest distance, and the portion having the shortest distance is not a point unit but a line unit ( In particular, it is preferable that a plurality of linear units be arranged. For example, it is preferable that the first extending portion 16b of the first electrode 16 and the predetermined portion of the second electrode 14 are arranged so as to have the shortest interval in a linear unit. As a result, it is possible to minimize light emission unevenness and to prevent the electrodes and elements from being destroyed.
For example, in FIG. 2, x1 to x3 can be about 40 to 100 μm, x4 can be about 40 to 100 μm, x5 can be about 40 to 100 μm, and x6 can be about 60 to 100 μm.

  With such a configuration, it is possible to effectively prevent the destruction of the electrode and the element. That is, in the conventional example (for example, FIG. 13), in the region (X in FIG. 13) corresponding to the first extending portion and the second extending portion and facing each other at the shortest distance, particularly the second extending portion. However, in the present invention, in the region where the two faces each other at the shortest distance (Y in FIG. 2), the first stretched portion is a relative ratio of a p-type semiconductor layer. Even if the electrode is connected to a layer having a high resistance, the destruction of the electrode in the vicinity of the first extending portion 16b of the p-electrode (16) and the destruction of the element in the semiconductor layer immediately below the first extending portion 16b are effectively prevented. can do.

  As another embodiment of the semiconductor light emitting device of the present invention, first and second electrodes are provided on the first and second conductivity type semiconductor layers, respectively, and the first and second electrodes are arranged on the same surface side. The first electrode includes a first pedestal portion and a first extending portion extending from the first pedestal portion so as to face the second electrode, the first extending portion. The part may extend in the element outer peripheral direction beyond the end part farthest from the first pedestal part in the opposing second electrode.

  In such a semiconductor light emitting device, the first electrode preferably has two or more first extending portions, and is electrically connected to the first conductivity type semiconductor layer through the translucent third electrode. It is preferable to be made. In the case where the first electrode has two or more first extending portions, a current can be supplied uniformly over the entire surface of the first conductivity type semiconductor layer. Furthermore, when the first electrode is electrically connected to the first conductive semiconductor layer via the translucent third electrode, the current is more efficiently applied to the entire surface of the first conductive semiconductor layer. Can be supplied, and uniform light emission can be obtained.

  Moreover, it is preferable that one of the first extending portions has a width different from that of the other first extending portion in the extending direction, and the first extending portion including the terminal portion farther from the first pedestal portion is formed by the first pedestal portion. It is preferable that the width is wider than the first extending portion including the close terminal portion. One of the first extending portions can be changed in width according to the distance from the first pedestal portion of the first extending portion when the width with respect to the extending direction is different from the other first extending portions, The current injected or extracted from the first pedestal electrode can be adjusted. In particular, when the first extending portion including the terminal portion farther from the first pedestal portion is wider than the first extending portion including the terminal portion closer to the first pedestal portion, the length depends on the length of the first extending portion. Therefore, the current flowing through the first extending portion can be made uniform.

  The second electrode includes a second pedestal portion and a second extending portion extending in the same direction as the first extending portion, or the outer periphery thereof is disposed surrounded by the first conductive semiconductor layer, or two or more are formed. It is preferable to be made. In the case where the second electrode includes the second pedestal portion and the second extending portion extending in the same direction as the first extending portion, the current is equal in the region where the second extending portion and the first extending portion face each other. In this region, it is possible to avoid the destruction of electrodes and elements due to heat. Further, when the second electrode is disposed so that the outer periphery is surrounded by the first conductive type semiconductor layer, the current spread from the first electrode in the surface direction is more efficiently increased from the entire periphery of the second electrode. Can be extracted. In addition, when two or more second electrodes are formed, current extraction can be performed more efficiently, and an area of the element can be increased.

  The second extending portion extends from the end of the second pedestal portion so that the shortest distance between the second pedestal portion and the first extending portion and the shortest interval between the second extending portion and the first extending portion are the same. Preferably it is. In this case, since the distance between the first extending portion of the first electrode and the second extending portion of the second electrode can be reduced, the current flow can be adjusted in the light emitting surface, and the first The shortest distance between the first stretched portion and the second stretched portion can be secured in a certain wide area.

  The first electrode and the second electrode have a shortest interval from the first extending portion to the second extending portion including the terminal portion farther from the first pedestal portion among the intervals from the first electrode to the second electrode. It is preferable that they are arranged in such a manner. Thereby, the space | interval of the 1st extending | stretching part and the 2nd extending | stretching part which were more distant from the 1st base electrode can be shortened, and the flow of an electric current can be adjusted within a light emission surface. In addition, a region where light emission is darker than other regions can be eliminated, and uniform light emission can be obtained.

Furthermore, it is preferable that the first extending portion and the second extending portion are arranged so that there are a plurality of points that are the shortest intervals. In this case, unevenness in light emission can be minimized, and destruction of electrodes and elements can be prevented.
In the outer peripheral region of the element, a plurality of protrusions protruding from the second conductive type semiconductor layer are formed, or in the outer peripheral region of the second electrode surrounded by the first conductive type semiconductor layer, the second conductive type is formed. It is preferable that a plurality of protrusions protruding from the semiconductor layer are formed. In these cases, light emitted from the end face of the semiconductor multilayer structure can be efficiently extracted to the upper surface.

  It is preferable that the first conductivity type semiconductor layer is a p-type nitride semiconductor layer and the second conductivity type semiconductor layer is an n-type nitride semiconductor layer. In this case, even in a p-type nitride semiconductor layer having a large specific resistance, the current can be more easily spread not only in the stacking direction of the semiconductor layer but also in the lateral direction perpendicular to the stacking direction. By flowing the current efficiently and uniformly, the semiconductor layer and the electrode can be prevented from being broken.

The first and second electrodes, optionally the third electrode, are, 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 conductivity 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. Note that the pedestal portion and the extending portion constituting the electrode are not necessarily integrally formed of the same material at the same time, and may have different materials and / or film thicknesses. In general, the pedestal portion preferably has a film thickness and an area necessary to function effectively for connection with the external electrode.

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 SiC (including 6H, 4H, 3C), an oxide substrate lattice-matched with ZnS, ZnO, GaAs, Si, and 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. On the substrate, in addition to the first and second conductivity type semiconductor layers, 5 such as a crystal nucleus forming layer, a low temperature growth buffer layer, a high temperature growth layer, a mask layer, and an intermediate layer may be formed as a base layer. .
In the first and second conductivity type semiconductor layers, the first conductivity type refers to p-type or n-type, and the second conductivity type refers to a conductivity type different from the first conductivity type, that is, n-type or p-type. Show. Preferably, the first conductivity type semiconductor layer is a p-type semiconductor layer, and the second conductivity type semiconductor layer is an n-type semiconductor layer.

The semiconductor layer is not particularly limited, and may be any of InAlGaP-based, InP-based, AlGaAs-based, mixed crystals thereof, and GaN-based nitride semiconductors. As the nitride semiconductor, GaN, AlN or InN, or a group III-V nitride semiconductor is a mixed crystal thereof _{(IIn X Al Y Ga 1-} XY N (0 ≦ X, 0 ≦ Y, X + Y ≦ 1)) 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. These semiconductor layers are usually doped with either n-type or p-type impurities.

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

  The second conductivity type semiconductor layer suitably contains an impurity and has a layer structure that realizes supply and diffusion of carriers in the electrode formation surface and the light emitting layer, and particularly from the electrode toward the light emitting layer. In order to supply carriers by in-plane diffusion, it is preferable to have a relatively highly doped contact layer. Furthermore, it is preferable to have an intervening layer that moves and supplies charges to the light emitting layer in the stacking direction, a clad layer that confines the second 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 first conductive semiconductor layer preferably has 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. 5, a GaN buffer layer 10 a and a non-doped GaN layer 10 b are stacked on a sapphire substrate 10, and Si serving as an n-type contact layer 11 a is formed as the second conductivity type semiconductor layer 11. A doped GaN layer, a Si-doped GaN layer serving as the n-type cladding layer 11b; an InGaN layer serving as the active layer 12, a Mg-doped AlGaN layer serving as the p-type cladding layer 13a as the first conductive semiconductor layer 13, and a p-type contact layer 13b The Mg-doped GaN layer has a layered structure that is sequentially stacked.

(Embodiment 2)
In the semiconductor light emitting device of the present invention, as shown in FIG. 3, a plurality of protrusions 29 protruding from the second conductivity type semiconductor layer may be formed in the outer peripheral region of the device. Thereby, the light radiate | emitted from the end surface of a semiconductor laminated structure can be taken out to an upper surface efficiently. Furthermore, as shown in FIG. 4, a plurality of protrusions 29 protruding from the second conductivity type semiconductor layer may be formed in the outer peripheral region of the second electrode surrounded by the first conductivity type semiconductor layer. Thereby, the light emitted from the end surface of the semiconductor laminated structure on the second electrode side can be efficiently extracted to the upper surface without being blocked by the second electrode.

  The protrusion may have any shape such as a quadrangle, trapezoid, or semicircle, but the trapezoid, that is, the truncated cone shape in which the protrusion 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 °, preferably 40 ° to 70 °. That is, light that has been projected from the light emitting layer to be totally reflected by the surface of the protrusion, or light that has been guided through the second conductivity type semiconductor layer 11 by being inclined so that the protrusion gradually becomes thinner toward the tip. As a result, light extraction toward the first 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 second semiconductor layer side). Thereby, when the light guided in the first semiconductor layer enters the inside of the protrusion, the light is easily emitted to the second 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 second 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 second conductivity type semiconductor layer is taken into the protrusion, and is extracted from the top of the protrusion or the middle part thereof, (2) The light guided in the second conductivity type semiconductor layer is irregularly reflected and extracted at the base of the protrusion, and (3) the light emitted laterally from the end face of the light emitting layer 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 first conductivity type semiconductor layer side by the unevenness. 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 that the lateral direction is increased. 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 performed over the entire region on the first 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 second conductivity type semiconductor layer, but the second conductivity 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 1st conductivity type semiconductor layer side.

  As shown in FIG. 5, the protrusion may 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 first conductivity type semiconductor layer, the tops thereof have substantially the same height, so that the first conductive material is not interrupted by the first electrode, which will be described later, from the top of the protrusions. Light can be effectively extracted to the mold semiconductor layer side. By configuring the protrusion to be higher than the first conductivity type semiconductor layer, preferably the first 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 1st 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.

(Embodiment 3)
In the semiconductor light emitting device of this embodiment, as shown in FIG. 6, the first electrode (16) is composed of only the first pedestal portion 16a and the two first extending portions 16b and 16c. The two electrodes (14) are substantially the same as in the first embodiment except that each of the second pedestal portion 14a and the second extending portion 14b is configured by one.

(Embodiment 4)
In the semiconductor light emitting device of this embodiment, as shown in FIG. 7, the p electrode (16) has only one first pedestal portion 16a, the first extending portions 16b and 16c, and the n electrode (14). Two second pedestal portions 14a and two second extending portions 14b are formed, respectively, and are substantially the same as those in the first embodiment except that the protrusion 29 is formed in the element outer peripheral region.
In this semiconductor light emitting element, the first extending portion 16b extends in the element outer peripheral direction beyond the end portion 14aa farthest from the first pedestal portion 16a in the second electrode 14. Further, the first extending portion 16b including the terminal portion 16bb farther from the first pedestal portion 16a is wider than the first extending portion 16c including the terminal portion 16cc closer to the first pedestal portion 16a.

The second extending portion 14b extends in the same direction as the first extending portions 16b and 16c, and the shortest distance (x7 in FIG. 7) between the second extending portion 14b and the first extending portion 16b and the second extending portion. The portion 14b and the first extending portion 16b extend from the end of the second pedestal portion 14a so that the shortest distance (x8 and x9 in FIG. 7) is the same.
For example, as shown in x7 to x11 in FIG. 7, the first electrode 16 and the second electrode 14 are arranged so that the distance between them is different. In FIG. 7, x10 and x11 have different intervals from x7 to x9, respectively. Among the intervals from the first electrode 16 to the second electrode 14, the second extending portion 14b of the second electrode 14 is the first one. The pedestal portion 16a is disposed with the shortest distance from the first extending portion 16b including the end portion 16bb that is further away (see the region from x8 to x9). For example, in FIG. 2, x1 to x3 can be 80 μm, x4 can be 85 μm, x5 can be 80 μm, and x6 can be 95 μm.

(Embodiment 5)
In the semiconductor light emitting device of this embodiment, as shown in FIG. 8, the tip of the second extending portion 14b is bent in the vertical direction, and the first electrode (16) facing the second extending portion 14b is extended. The distance to the part 16c (x12 in FIG. 8) is the same as that of the fourth embodiment except that it is the same as x9.
Further, in addition to FIG. 7, a plurality of protrusions 29 (n dimples) protruding from the second conductivity type semiconductor layer are formed in the outer peripheral region of the n electrode (14).

(Experimental example 1)
In FIG. 2, an element having x1 to x3 of about 80 μm, x4 of about 85 μm, x5 of about 80 μm, and x6 of about 95 μm is formed. A large current of 2 A was applied, and the time until the device was destroyed was examined.
As a result, it was 7.6 seconds for the device of FIG.
On the other hand, for the device shown in FIG. 13 as a comparative example (the same chip size as the device of FIG. 2), when a large current was passed in the same manner, the time until the device was destroyed was 6.5 seconds. It cracked in two in the direction perpendicular to the stretched part.

(Experimental example 2)
In FIG. 3, an element having a size corresponding to about 80 μm, x4 is about 85 μm, x5 is about 80 μm, and x6 is about 95 μm is formed. The relationship with improved efficiency was measured.
As a result, in the device of FIG. 3, the forward voltage was 3.52 V at 350 mA. In addition, the current density was 18.6 lm / W at 78.6 A / cm ² , and the light emission efficiency was high at a high current density.
On the other hand, in the device of FIG. 13 used in Experimental Example 1, the forward voltage was 350 mA, which was about 4 to 5% higher than that of the device of FIG. The current density was 78.6 A / cm ^2, which was about 7 to 8% lower than that of the device shown in FIG.

(Experimental example 3)
In FIG. 4, x1 to x3 were about 80 μm, x4 was about 85 μm, x5 was about 80 μm, and x6 was about 95 μm, and Vf was measured.
As a result, in the element shown in FIG. 4, the forward voltage increase of about 0.044 V can be stopped for 60 seconds after the operation, which is considered to be related to the element deterioration due to heat.
On the other hand, in the device of FIG. 13 used in Experimental Example 1, a forward voltage increase of about 0.124 V, about 3 times that of the device of FIG.

(Simulation experiment example 1)
For the element of FIG. 2 similar to Experimental Example 1, the current density distribution was simulated by changing only x6 of FIG. The results are shown in FIGS.
In the case of the arrangement as shown in FIG. 2, the current density spreads almost uniformly over the entire element with the vicinity of the second electrode as a peak (FIG. 9). However, when x6 is reduced and the second pedestal portion of the second electrode is brought closer to the element outer peripheral direction, a region having a high current density is concentrated in the vicinity of the element outer periphery (FIG. 10). On the other hand, as x6 is increased to bring the second pedestal portion closer to the first pedestal portion, the current density in the vicinity of the second electrode increases, and the distance between the second pedestal portion and the first pedestal portion is When arranged so as to be smaller than the distance between the second pedestal and the outer periphery of the element, the current density in the vicinity of the outer periphery of the element became lower than that in the other parts (FIG. 11).

(Simulation experiment example 2)
For the element of FIG. 2 similar to Experimental Example 1, only the lengths of the first extending portions 16b and 16c of FIG. 2 were changed, and a simulation was performed to obtain a current density distribution and a potential difference.
The length of the first extending portion was shortened by 50 μm to 250 μm with reference to the length of the first extending portions 16b and 16c shown in FIG. When the reference is used and when it is 50 μm shorter than the reference, the first extending portion extends in the element outer peripheral direction beyond the end farthest from the first pedestal portion of the second electrode, and is shorter than the reference by 100 μm or more. When it did, the termination | terminus part of the 1st extending | stretching part was arrange | positioned rather than the edge part of the 2nd electrode at the 1st base part side.
FIG. 12 shows the forward voltage calculated from the potential difference. In FIG. 12, the horizontal axis indicates the length of the first stretched portion by a difference from the reference, and the vertical axis indicates the expected forward voltage by the difference from the reference. As shown in FIG. 12, the forward voltage is expected to increase as the first stretched portion becomes shorter, but the first stretched portion extends beyond the second electrode in the element outer peripheral direction up to about 50 μm. It is thought that it hardly increases.
In addition, when the terminal portion of the first extending portion is disposed closer to the first pedestal portion than the end portion of the second electrode, the current density is high from the second electrode toward the terminal portion of the first extending portion. Tended to concentrate.

  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 sectional drawing for demonstrating the structure of the semiconductor light-emitting device of this invention. It is a schematic plan view for demonstrating the 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. It is a schematic plan view for demonstrating another structure of the semiconductor light-emitting device of this invention. FIG. 4 is a sectional view taken along line B-B ′ in FIG. 3. It is a schematic plan view 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. It is a schematic plan view for demonstrating another structure of the semiconductor light-emitting device of this invention. FIG. 6 is a diagram showing a current density distribution of the semiconductor light emitting device of Simulation Example 1. FIG. 6 is a diagram showing a current density distribution of the semiconductor light emitting device of Simulation Example 1. FIG. 6 is a diagram showing a current density distribution of the semiconductor light emitting device of Simulation Example 1. 6 is a graph showing the relationship between the length of the first extending portion of the semiconductor light emitting element of Simulated Experiment Example 2 and the expected forward voltage. It is a schematic plan view for demonstrating the structure of the conventional semiconductor light-emitting device.

Explanation of symbols

10 sapphire substrate 10a GaN buffer layer 10b non-doped GaN layer 11 second conductivity type semiconductor layer 11a n type contact layer 11b n type cladding layer 12 light emitting layer 13 first conductivity type semiconductor layer 13a p type cladding layer 13b p type contact layer 14 first 2 electrode 15 3rd electrode 16 1st electrode 16a 1st base part 16b, 16c 1st extending | stretching part 14aa End part 16bb, 16cc Terminating part 29 Protrusion part

Claims (4)

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 first electrode includes a first pedestal portion and at least two first extending portions extending in the same direction from the first pedestal portion, and the second electrode includes a second pedestal portion and the second pedestal portion. A second extending portion extending in substantially the same direction as the first extending portion so as to approach the first pedestal portion from the pedestal portion;
Each of the at least two first extending portions has a terminal portion disposed in the outer peripheral direction of the second electrode beyond the end portion farthest from the first pedestal portion in the same direction portion, The first extending part is provided with the first pedestal part in the same direction part, and the other first extending part is arranged so that the distance between the first electrode and the second electrode is the shortest in the same direction part,
The second extending portion includes a shortest distance between the same direction portion of the other first extending portion and the second pedestal portion, and the same direction portion of the other first extending portion and the second extending portion. A semiconductor light emitting element, wherein the semiconductor light emitting element is extended from the second pedestal so that the shortest interval is the same. Two or more second electrodes are formed;
The first electrode has three first extending portions,
The three first extending portions have one first extending portion in which only one first pedestal portion is provided in the same direction portion, and the distance between the first electrode and the second electrode is the shortest in the same direction portion. Two other first extending portions arranged so as to be, or one first extending portion arranged so that the distance between the first electrode and the second electrode is the shortest in the same direction portion, The semiconductor light emitting element according to claim 1, which is another two first extending portions each having a first pedestal portion provided in the same direction portion.   3. The semiconductor light emitting element according to claim 1, wherein a distance between the second pedestal portion and the first pedestal portion is equal to or greater than a distance between the second pedestal portion and the outer periphery of the element. A light emitting layer is provided between the second conductive type semiconductor layer and the first conductive type semiconductor layer, and the second conductive type semiconductor layer includes the first conductive type semiconductor layer and the light emitting in a part of the region. The layer is removed and its surface is exposed,
The semiconductor light-emitting element according to claim 1, wherein the second electrode is provided on the exposed surface, and an outer periphery thereof is disposed so as to be surrounded by the first conductive semiconductor layer.

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