JP4134573B2 - Semiconductor light emitting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor light emitting device, and more particularly, a structure in which a semiconductor layer having a light emitting junction and an electrode for applying a bias to an n-type region and a p-type region of the semiconductor layer are formed on the same surface side of a support substrate. The present invention relates to a semiconductor light emitting device having the same.
[0002]
[Prior art]
Conventionally, as shown in, for example, JP-A-9-36422, JP-A-8-228048, JP-A-10-93138, etc., an n-type region and a p-type region are laminated on the same surface side of a support substrate to emit light. 2. Description of the Related Art A semiconductor light emitting element having a structure in which a semiconductor layer having a junction is formed and an electrode for applying a bias to the semiconductor layer is formed on the same side of a supporting substrate is known.
[0003]
In these conventional semiconductor light emitting devices, a sapphire substrate is used as a supporting substrate, an n-type contact layer is stacked on the sapphire substrate via a buffer layer, and a light emitting semiconductor layer having a light emitting junction layer (active layer), a p-type contact layer Have a layer structure in which are sequentially stacked. In the light emitting semiconductor layer, an n-type clad layer and a p-type clad layer made of a group III nitride semiconductor are arranged on the lower and upper sides, and a light emitting junction is formed at the boundary between them. Further, on the n-type contact layer, a part of the p-type contact layer and the light emitting semiconductor layer is removed by etching until the n-type contact layer is exposed, so that a region where the n-type contact layer is exposed becomes the light emission. It is formed adjacent to the stacked region of the semiconductor layers. In the exposed region of the n-type contact layer, a one-letter-shaped electrode is formed so as to face the light-emitting semiconductor layer with a space in plan view, while the one-letter-shaped electrode is also formed in the p-type contact layer. It is formed to be parallel to the electrode in the exposed region. Then, by applying a forward bias to the light emitting semiconductor layer (a positive voltage is applied to the electrode of the p-type contact layer), the electrode provided on the p-type contact layer is exposed to the exposed portion of the n-type contact layer. A current flows toward the provided electrode, and holes and electrons combine in the light emitting junction layer in the light emitting semiconductor layer to emit light.
[0004]
[Problems to be solved by the invention]
By the way, in the conventional semiconductor light emitting device as described above, when a forward bias is applied between the electrodes, the current flowing in the light emitting semiconductor layer has a region in which the resistance is relatively small in the light emitting semiconductor layer. There is a tendency to flow mainly. That is, the resistance in the light emitting semiconductor layer becomes smaller as the distance through which the current flows in the light emitting semiconductor layer becomes shorter. Therefore, the current flows between the electrode of the p-type contact layer and the electrode provided on the exposed portion of the n-type contact layer. It flows mainly in the area between. Therefore, as described above, in the conventional semiconductor light emitting device, the electrode of the p-type contact layer and the electrode of the n-type contact layer are formed in one letter parallel to each other on the same surface side of the support substrate. In the light emitting junction layer, the region where the current flows and emits substantially intense light is shifted to the portion interposed between the two electrodes, and the entire light emitting junction layer cannot be used as the light emitting region, and the light emission intensity is reduced as a whole. There is a problem that it ends up.
[0005]
In order to alleviate this problem, if the position of the electrode of the p-type contact layer is positioned far from the electrode of the n-type contact layer in the conventional semiconductor light emitting device, the size of the light emitting junction layer that can be used as the light emitting region is On the other hand, the distance that current flows through the light emitting semiconductor layer is increased, resulting in a problem that a resistance value is increased and a power loss is caused.
[0006]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a semiconductor layer having a light emitting junction and electrodes for applying a bias to the n-type region and the p-type region of the semiconductor layer, respectively, on the same support substrate. An object of the present invention is to provide a semiconductor light emitting device capable of improving light emission intensity and preventing power loss even with a structure formed on the surface side.
[0007]
[Means for Solving the Problems]
The semiconductor light emitting device of the present invention has the following configuration in order to achieve the above object. That is, the semiconductor light emitting device of the present invention includes a support substrate, and a first contact layer of the first conductivity type is laminated on the support substrate. On the first contact layer, a light emitting semiconductor layer in which a first conductivity type clad and a second conductivity type clad are arranged at a lower layer and an upper layer and a light emitting junction is formed at the boundary is laminated. A second conductivity type second contact layer is stacked on the light emitting semiconductor layer. The first contact layer is formed in a shape divided into a plurality of blocks on the first contact layer, and is positioned parallel to a boundary portion between the light emitting semiconductor layer and the exposed region of the first contact layer. A first electrode is formed. On the second contact layer, it has a rod shape and is provided at substantially equal intervals, and crosses the first electrode so that the distance between one end thereof and the first electrode is substantially equal. A second electrode is formed which includes a rod-shaped electrode piece arranged in the direction to be connected and an electrode connecting portion for electrically connecting each of the rod-shaped electrode pieces.
[0008]
Note the first conductivity type and the second conductivity type, I Oh intended to mean any conductive type of the n-type or p-type in the counter electrode, for example if one is n-type while the other becomes a p-type . In addition, the exposed region of the first contact layer may not necessarily exist in a state where it is finally exposed directly to the atmosphere as long as the first electrode is directly formed. For example, the first electrode After the formation, the surface may be coated with a material that does not inhibit light emission of the semiconductor light emitting element and does not affect the physical or chemical characteristics of the element.
[0009]
In the present invention, when a forward bias is applied, a path of current flowing in the light emitting semiconductor layer is formed between the rod-shaped electrode piece of the second electrode and the first electrode. becomes, but since at this time the plurality of rod-shaped electrode pieces each and each tip thereof spaced apart at equal intervals has a front Symbol substantially equal distances of the first electrode, the first and the rod-shaped electrode pieces A current path is formed substantially uniformly without being shifted to a specific location between the electrodes. Further, since the rod-shaped electrode piece extends in a direction approaching from a position far from the first electrode , the position of the second electrode is positioned far from the first electrode on the second contact layer. Even if it is not disposed, the electrode peripheral length of light emission can be lengthened to enlarge the region contributing to light emission in the light emitting bonding layer. As a result, the light emitting efficiency of the semiconductor light emitting device of the present invention can be improved as a whole, and power loss does not occur.
[0011]
In the semiconductor light emitting device of the present invention, it is preferable that the width of the rod-shaped electrode piece is narrowed toward the tip. In this case, the equipotential surface of the second electrode with respect to the first electrode is distributed like the pattern shape of the electrode, that is, the shape of the rod-shaped electrode piece whose width decreases toward the tip. At this time, since the current flows in parallel to the electric field lines orthogonal to the equipotential surface, the current flowing between the first and second electrodes has the width of the rod-shaped electrode piece narrowed toward the tip side. As a result, current does not concentrate only at the tip of the rod-shaped electrode piece that is closest to the first electrode, but also flows between the sides of the adjacent rod-shaped electrode pieces. As a result, the luminous efficiency can be further improved.
[0012]
In the semiconductor light emitting device of the present invention, a plurality of the exposed regions may be formed on the first contact layer so as to sandwich the light emitting semiconductor layer. In this case, if the first electrode is formed in each of the exposed regions formed so as to sandwich the light emitting semiconductor layer and the opposing relationship between the first and second electrodes as described above is realized, the light emission Since the semiconductor layer can expand the light emitting region from both sides of the semiconductor layer, the light emission efficiency can be further improved.
[0013]
Furthermore, in this case, a plurality of the exposed regions and a plurality of the light emitting semiconductor layers may be alternately arranged on the first contact layer. By doing in this way, the opposing relationship of the 1st and 2nd electrodes as mentioned above can be repeatedly realized in the same element, and the luminous efficiency can be further improved.
[0014]
Further, in the semiconductor light-emitting device of the present invention, the first electrode is formed in a shape that is divided into blocks of several to and face the intermediate position of the tip of the rod-shaped electrode pieces each block to adjacent as that has been placed. In this case, each block of the first electrode has the same distance from each tip of the rod-shaped electrode pieces adjacent to each other, and the current between each rod-shaped electrode piece and the first electrode in the second electrode is It can be made more uniform.
[0015]
Moreover, in this invention, it is preferable when the front-end | tip part of the said rod-shaped electrode piece is provided with roundness. That is, the current tends to be concentrated at the corners, so that the current concentration can be prevented by rounding the tip, and the current can be made more uniform.
[0016]
In the present invention, the support substrate is a sapphire substrate, the first contact layer is formed on the support substrate via a buffer layer, and the light emitting semiconductor layer is formed of a group III nitride semiconductor. It is particularly useful when applied in devices. That is, in the semiconductor light emitting device having such a material structure, since the electrode for applying a bias to the light emitting semiconductor layer is usually formed on the same surface side of the support substrate, the effect of the present invention appears more remarkably. Because.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
[0018]
Figure 1 is a perspective view showing a semiconductor light emitting device according to a reference example of the present invention, FIG. 2 is a plan view of a semiconductor light - emitting element shown in FIG.
[0019]
In the semiconductor light emitting device according to the reference example , an insulating sapphire substrate is used as the support substrate 1, and a first contact layer 2 made of n-type GaN is stacked on the support substrate 1 with a buffer layer 7 interposed therebetween. Is formed. The buffer layer 7 is provided to alleviate the lattice mismatch between the sapphire substrate and the n-type GaN, and is formed of, for example, GaN, AlGaN, AlN or the like.
[0020]
A light emitting semiconductor layer 3 having a light emitting junction 33 is stacked on the n-type contact layer 2. The light emitting semiconductor layer 3, which has been formed using a group III nitride semiconductor, n-type cladding layer 31 to the lower, has a p-type cladding layer 32 to the upper, the light emitting junction 33 of these It is formed at the boundary between the cladding layers 31 and 33. The n-type cladding layer 31, the light emitting junction 33, and the p-type cladding layer 32 can be formed by sequentially stacking, for example, n-type AlGaN, n-type InGaN, and p-type AlGaN. When the light emitting junction 33 is formed of n-type InGaN, the emission color of the light emitting junction 33 is adjusted by appropriately adjusting the composition ratio of In or by using n-type impurities such as Si, Ge, and S, Zn, Mg, and the like. By appropriately doping p-type impurities, the desired color can be adjusted in the ultraviolet to red range. A second contact layer 2 made of p-type GaN is stacked on the light emitting semiconductor layer 3.
[0021]
In this reference example , on the first contact layer 2, a region 21 where the surface of the first contact layer 2 is exposed is formed next to the region where the light emitting semiconductor layer 3 is laminated as described above. For example, the exposed region 21 corresponds to the exposed region 21 of the light emitting semiconductor layer 3 and the second contact layer 2 after the light emitting semiconductor layer 3 and the second contact layer 2 are stacked over the entire surface of the first contact layer 2. It is preferable to form the portion laminated on the portion by etching until the first contact layer 2 is exposed. In this reference example , the region where the light emitting semiconductor layer 3 is laminated on the first contact layer 2 and the exposed region 21 are rectangular adjacent to each other on the long side. 2 indicates a boundary between the light emitting semiconductor layer 3 and the p-type contact layer 4 and the exposed region 21.
[0022]
On the exposed region 21, a single-letter-shaped first electrode 5 is formed. The first electrode 5 is opposed to the side wall surface of the light emitting semiconductor layer 3 rising at the boundary A with a space therebetween, and its longitudinal direction extends in parallel along the boundary A.
[0023]
On the other hand, a second electrode 6 is formed on the p-type contact layer 4. The second electrode 6 has three rod-shaped electrode pieces 61 extending in a direction orthogonal to the first electrode 5 and spaced in parallel at equal intervals. These three rod-shaped electrodes The piece 61 is formed in a so-called comb-like shape in which an end portion at a position far from the first electrode 5 is connected by a one-letter-shaped electrode connecting portion 62. The tip portions of the three rod-shaped electrode pieces 61 projecting in the direction approaching the first electrode 5 from the electrode connecting portion 62 are substantially equal in distance to the first conductivity type electrode. In addition, although not shown in figure, the front-end | tip part of this rod-shaped electrode piece 61 can also provide roundness. In this case, the current tends to be concentrated at the corners, so that the current concentration can be prevented by rounding the tip, and the current can be made more uniform.
[0024]
The first electrode 5 and the second electrode 6 can be formed by using a predetermined mask so as to have the above-mentioned shape. As an electrode material, for example, a metal such as Ni, Al, Au, Ti, or the like is used. It is good to use.
[0025]
In the semiconductor light emitting device of this reference example, when a positive voltage is applied to the second electrode 6 formed in the forward contact, that is, the p-type second contact layer, a hole is formed at the light emitting junction 33 in the light emitting semiconductor layer 3. Electrons combine to emit light. At this time, a path of a current flowing in the light emitting semiconductor layer 3 is formed between the three rod-shaped electrode pieces 61 and the first electrode 5, but the three rod-shaped electrode pieces 61 are equally spaced from each other. And their tips are equidistant from the first electrode 5, so that the current flows uniformly to the rod-shaped electrode pieces 61. Further, since the rod-shaped electrode piece 61 extends in a direction orthogonal to the first electrode 5, a region that contributes to light emission in the light-emitting bonding layer 33 by extending the length of the electrode that is remarkably light-emitting is defined as the first electrode. It is possible to expand to a region far from 5 and to improve the light emission efficiency of the entire light emitting element. Moreover, since the tip of the rod-shaped electrode piece 61 is present at a position close to the first electrode 5, the resistance value can be relatively small and no power loss occurs.
[0026]
FIG. 3 is a plan view showing a semiconductor light emitting device according to another reference example . In this reference example, there are four rod-shaped electrode pieces 61, and the two outermost rod-shaped electrode pieces 61 are arranged so as to correspond to both end positions of the first electrode 5, respectively, as shown in FIG. This is different from the above-mentioned reference example .
[0027]
In this reference example , the length of the second electrode 6 facing the first electrode 5 is the longest, that is, all the rod-shaped electrode pieces 61 are arranged within the full length of the first electrode 5. Therefore, the first electrode 5 can be used as a current source passing through the light emitting junction layer 33 without leaving the length of the first electrode 5, and the light emission efficiency can be further improved.
[0028]
FIG. 4 is a plan view showing a semiconductor light emitting device according to still another reference example . This reference example is different from the above-described reference example shown in FIG. 3 in that the rod-shaped electrode piece 61 has a shape that narrows toward the tip.
[0029]
In this reference example, since the stick-shaped electrode pieces 61 are narrowed in width toward the distal end side, the side of the rod-shaped electrode pieces 61 are oblique rather than perpendicular direction to the first electrode 5. Since the equipotential surface of the second electrode is distributed like the pattern shape of the electrode, in the rod-shaped electrode piece 61, the equipotential surface is distributed on the side portion as well as the tip portion. When a bias is applied, the current flow in the second electrode flows in parallel to the electric field lines orthogonal to the equipotential surface, so that the tip of the rod-shaped electrode piece 61 that is closest to the first electrode 5 is used. The current flows between the side edges of the adjacent bar-shaped electrode pieces 61, 61 without being concentrated only on the side. As a result, the luminous efficiency can be further improved.
[0030]
FIG. 5 is a plan view showing a semiconductor light emitting device according to still another reference example . In this reference example , two exposed regions 21 are formed on the contact layer 2 so as to sandwich the light emitting semiconductor layer 3, and the first electrode 5 having a single character is formed in each of the two exposed regions 21. In the second electrode 6 on the contact layer 2, each rod-shaped electrode piece 61 is connected by an electrode connecting portion 62 at the approximate center of the contact layer 2, and each protruding from the electrode connecting portion 62 toward the left and right sides. Each of the rod-shaped electrode pieces 61 is different from the above-described reference example shown in FIG. 4 in that the width is narrowed toward the tip side.
[0031]
In the present reference example , the light emitting semiconductor layer 3 is sandwiched between the two exposed regions 21, so that the opposing relationship between the first electrode 5 and the second electrode 6 as described in the above reference example is established. Since the light emitting region can be enlarged from both the left and right sides of the light emitting semiconductor layer 3, the light emission efficiency can be further improved.
[0032]
FIG. 6 is a plan view showing a semiconductor light emitting device according to still another reference example . In this reference example, there are three exposed regions 21 and two light emitting semiconductor layers 3 on the contact layer 2, and these are alternately arranged, which is different from the above-described reference example shown in FIG. Is different.
[0033]
In the present reference example , the light emitting structure of the light emitting semiconductor layer 3 as described in the reference example shown in FIG. 5 is realized at a plurality of locations in the same element, and the light emission efficiency can be further improved.
[0034]
FIG. 7 is a plan view showing the semiconductor light emitting device according to the first embodiment. This embodiment is different from the above-described reference example shown in FIG. 4 in that the first electrode 5 is formed in a shape divided into a plurality of blocks 51 instead of a single character. Each block 51 is arranged so as to face the intermediate position of the tip of the adjacent bar-shaped electrode piece. Although not shown, each block 51 is connected to have the same potential.
[0035]
In the present embodiment, each block 51 of the first electrode 5 has the same distance from each tip of the rod-shaped electrode pieces 61 adjacent to each other. The current between the electrodes 5 can be made more uniform.
[0036]
As described above, in the semiconductor light-emitting device according to claim 1, and the tips thereof are a plurality of rod-shaped electrode pieces spaced at each equal interval with the second electrode instead character shaped Since the first electrode divided into a plurality of blocks is substantially equidistant, and each of these blocks is disposed so as to face the intermediate position of the tip of the adjacent bar-shaped electrode piece, the forward bias Is applied, a current path is formed substantially uniformly between each rod-shaped electrode piece and the first electrode without being shifted to a specific location. Further, since the rod-shaped electrode piece extends in a direction approaching from a position far from the first electrode, the second electrode is disposed at a position far from the first electrode on the second contact layer. Even if it does not, the area | region which contributes to light emission in the said light emitting joining layer can be expanded by lengthening the electrode periphery length with remarkable light emission. As a result, the semiconductor light emitting device of the present invention can improve the light emission efficiency as a whole, and has the effect of causing no power loss. Each block has the same distance from each tip of the bar electrode pieces adjacent to each other, and the current between the bar electrode pieces and the first electrode in the second electrode can be made more uniform. it can.
[0038]
In the semiconductor light emitting device according to claim 2 , in the invention of claim 1 , since the width of the rod-shaped electrode piece is narrowed toward the tip, the distance from the first electrode is the shortest. The current does not concentrate only on the tip of the rod-shaped electrode piece, but also flows between the sides of the adjacent rod-shaped electrode pieces. As a result, the luminous efficiency can be further improved.
[0039]
In the semiconductor light emitting device according to claim 3 , in the invention according to any one of claims 1 to 2 , the plurality of exposed regions are formed on the contact layer so as to sandwich the light emitting semiconductor layer. The light emitting region can be expanded from both directions sandwiching the light emitting semiconductor layer, and the light emission efficiency can be further improved.
[0040]
In the semiconductor light emitting device according to claim 4 , in the invention of claim 3 , the plurality of exposed regions and the plurality of light emitting semiconductor layers are arranged alternately on the contact layer. The light emitting region can be expanded by the plurality of light emitting semiconductor layers in the element, and the light emission efficiency can be further improved.
[0042]
In the semiconductor light emitting device according to claim 5 , in the invention of any one of claims 1 to 4 , the tip of the rod-shaped electrode piece is rounded. Current concentration at the corner can be prevented, and current can be made more uniform.
[0043]
The semiconductor light-emitting device according to claim 6 is the semiconductor light-emitting device according to any one of claims 1 to 5 , wherein the support substrate is a sapphire substrate, and the first contact layer is supported via a buffer layer. By forming the light emitting semiconductor layer on a substrate and forming the group III nitride semiconductor, the effect of the present invention becomes more remarkable.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a semiconductor light emitting device according to a reference example of the present invention.
FIG. 2 is a plan view of the semiconductor light emitting device of the reference example .
FIG. 3 is a plan view of a semiconductor light emitting device according to another reference example of the present invention.
It is a plan view of a semiconductor light emitting device according to still another reference example of the present invention; FIG.
FIG. 5 is a plan view of a semiconductor light emitting element according to still another reference example of the present invention.
FIG. 6 is a plan view of a semiconductor light emitting device according to still another reference example of the present invention.
FIG. 7 is a plan view of the semiconductor light emitting element according to the first embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Support substrate 2 1st contact layer 21 Exposed area | region 3 Light emitting semiconductor layer 31 N-type clad (1st conductivity type clad)
32 light emitting junction 33 p-type cladding (second conductivity type cladding)
4 Second contact layer 5 First electrode 6 Second electrode 61 Rod-shaped electrode piece

Claims (6)

A support substrate, and a first contact layer of a first conductivity type laminated on the support substrate;
The first contact layer is laminated on the first contact layer so that a part of the first contact layer is exposed in a rectangular shape, and the first conductivity type cladding and the second conductivity type cladding are arranged on the lower and upper sides, respectively, at the boundary between them. A light emitting semiconductor layer having a light emitting junction formed thereon;
A second contact layer of a second conductivity type laminated on the light emitting semiconductor layer;
A first electrode formed substantially in a letter on the first contact layer and positioned parallel to a boundary portion between the light emitting semiconductor layer and the exposed region of the first contact layer;
A rod-like shape is provided on the second contact layer so as to be spaced apart from each other at substantially equal intervals, and intersects the first electrode so that the distance between one end and the first electrode is substantially equal. A second electrode comprising: a rod-shaped electrode piece disposed on the electrode; and an electrode connecting portion that electrically connects each of the rod-shaped electrode pieces;
The first electrode is formed in a shape in which a single character is divided into a plurality of blocks, and each block is disposed at a position facing an intermediate position of a straight line connecting the one ends of the adjacent rod-shaped electrode pieces. A semiconductor light emitting element characterized by being made. 2. The semiconductor light emitting element according to claim 1, wherein the width of the rod-shaped electrode piece is narrowed toward the tip . It said plurality of said exposed region in the first contact layer is, the semiconductor light-emitting device according to claim 1 or 2, characterized in that it is formed so as to sandwich the light emitting semiconductor layer. 4. The semiconductor light emitting element according to claim 3, wherein a plurality of the exposed regions and a plurality of the light emitting semiconductor layers are alternately arranged on the first contact layer . The semiconductor light emitting element according to claim 1, wherein a tip end portion of the rod-shaped electrode piece is rounded . The support substrate is a sapphire substrate, the first contact layer is formed on the support substrate through a buffer layer, and the light emitting semiconductor layer is formed of a group III nitride semiconductor. Item 6. The semiconductor light emitting device according to any one of Items 1 to 5 .

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