JP3960636B2 - Light emitting element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light emitting element such as a light emitting diode.
[0002]
[Prior art]
Recently, light-emitting elements made of gallium nitride semiconductors such as GaN, GaAlN, InGaN, and InAlGaN have been actively researched and developed because they can emit blue light with a strong intensity such as blue.
[0003]
However, in general, an insulating substrate such as sapphire is used in such a light emitting element made of a gallium nitride semiconductor.
[0004]
In the light emitting element using this insulating substrate, it is difficult to make a structure in which one electrode is provided on the back surface of this substrate, and both the p-type side and the n-type side electrode are provided on the semiconductor layer side (same surface side). Structure is adopted.
[0005]
Such a light emitting element having both electrodes on the semiconductor layer side is described in, for example, Japanese Patent Application Laid-Open No. 6-338632 (H01L 33/00).
[0006]
FIG. 4 is a schematic top view (semiconductor layer side) of a conventional light emitting diode, and FIG. 5 is a schematic cross-sectional view along the alternate long and short dash line AA in FIG.
[0007]
4 and 5, 101 is a sapphire substrate, 102 is an n-type GaN layer, 103 is a p-type GaN layer, 104 is an n-type side electrode formed on the n-type GaN layer 102, and 105 is a p-type GaN layer 103. A translucent p-type side electrode 106 formed above is a bonding pad formed at the corner of the p-type side electrode 105.
[0008]
In this light emitting diode, light is extracted from the p-type side electrode 105 side.
[0009]
[Problems to be solved by the invention]
However, since the n-type side electrode 104 exists only at the corner of the n-type GaN layer 102 in the light emitting diode, current does not flow uniformly throughout the n-type GaN layer 102.
[0010]
As a result, in the conventional light emitting diode, there is a possibility that the light emitting region is narrow and the element is deteriorated due to current concentration.
[0011]
The present invention has been made in view of the above-described problems, and an object thereof is to provide a light-emitting element including a p-type side electrode and an n-type side electrode on the semiconductor layer side having a large light emitting region.
[0012]
[Means for Solving the Problems]
The light emitting device of the present invention includes a substrate and a plurality of semiconductor layers grown on the substrate, and the first electrode for the first conductivity type side and the second electrode for the second conductivity type side on the semiconductor layer side. The first electrode is located substantially over the entire top layer of the first conductivity type among the plurality of semiconductor layers, and the second electrode is located around the top layer. In the light emitting element located on the second conductivity type semiconductor layer of the plurality of semiconductor layers, the second electrode is formed in an L shape around the electrode region of the first electrode, A bonding pad portion is provided at the approximate center of the L-shape .
[0015]
The first electrode is made of a translucent metal electrode.
[0016]
In particular, the first electrode is a linear metal electrode.
[0017]
Further, the first electrode is set to have a light-transmitting thickness.
[0018]
In addition, the first electrode is wire-bonded at the corner, and the second electrode is wire-bonded at the bonding pad portion of the second electrode substantially diagonal to the corner. It is characterized by.
[0019]
Further, the second electrode is characterized in that it is arranged in a shape that is equidistant from the bonding portion of the first electrode.
[0020]
In particular, the second electrode has a substantially half circumference around the electrode region of the first electrode.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
A light-emitting diode according to an embodiment of the present invention will be described with reference to the drawings. 1 and 2 are a schematic top view (semiconductor layer side) of the light-emitting diode, and a schematic cross-sectional view taken along one-dot chain line AA in FIG.
[0022]
1 and 2, an n-type GaN layer 2 having a layer thickness of 3 μm and a p-type GaN layer 3 having a layer thickness of 1 μm are stacked in this order on an insulating substrate 1 such as sapphire. The n-type layer 2 is exposed by etching away.
[0023]
A light-transmitting substantially square p-type side electrode (first electrode) 4 made of Ni having a thickness of 100 mm is formed on substantially the entire area of the p-type GaN layer (uppermost layer) 3, and its end A bonding pad 5 made of Au having a film thickness of 1 μm is formed in the part.
[0024]
On the exposed surface of the n-type layer 2, there is an L-shaped portion (one opposing periphery of the region) around the electrode region of the substantially rectangular p-type side electrode 4 so as to oppose the bonding pad 5. An n-type side electrode (second electrode) 6 made of Al having a layer thickness of 1 μm and having a bonding pad portion 6b at the approximate center thereof is provided around each side-side region portion 6a.
[0025]
Although not shown, bonding wires made of Au or the like (not shown) are bonded to the bonding pad 5 and the bonding pad portion 6b, respectively, and are electrically connected to a lead frame or the like.
[0026]
The p-type side electrode 4 has a light-transmitting property with respect to the light emission by setting the thickness so that the light emission is transmitted, and the p-type side electrode 4 side becomes the light extraction side.
[0027]
The p-type side electrode 4 is formed in substantially the entire region on the p-type GaN layer 3 so that current flows substantially uniformly on the p-type side, and the n-type side electrode 6 is also configured as a p-type side electrode. By forming an L shape so as to surround the periphery of the region 4, the n-type side is also configured to allow current to flow more uniformly. As a result, the current flows in a large area and substantially uniformly in the element including the light emitting region (pn junction surface), so that the light emitting area is large and current concentration does not occur substantially.
[0028]
In addition, in this embodiment, since the bonding pad 5 and the bonding pad portion 6b are located at the corners on the diagonal line of the element, the current flowing in the element becomes more uniform.
[0029]
A light-emitting diode according to another embodiment of the present invention will be described with reference to FIG. 3 which is a schematic top view (semiconductor layer side). In addition, since it is the same as that of the said embodiment except a p-type side electrode, the description is omitted.
[0030]
In FIG. 3, on the p-type GaN layer 3, a film thickness of 0.1 mm is formed of an electrode portion 13 in which a linear electrode portion extends radially from a substantially center and a bonding pad 5 integrally connected to one end thereof. A p-type side electrode (first electrode) 14 having an Au / Ni structure is formed by laminating a 1 μm Ni film and a 0.7 μm thick Au film in this order.
[0031]
On the exposed surface of the n-type layer 2, around the electrode region (inside the dotted line in the drawing) 15 of the substantially square p-type side electrode 14 so that the bonding pad 5 is desired as in the above embodiment, An n-type side electrode 6 made of Al having a layer thickness of 1 μm and having a bonding pad portion 6b at the substantially center thereof is formed in an L-shaped portion (one opposing side region portion around the region) 6a. It is installed.
[0032]
The p-type side electrode 14 has a linear shape so as to transmit light, and thus has light-transmitting properties with respect to light emission, and the p-type side electrode 14 side becomes a light extraction side.
[0033]
The p-type side electrode 14 is configured so that a current flows substantially uniformly on the p-type side because the electrode region 15 is substantially the entire region on the p-type GaN layer 3, and the n-type side electrode 6 is also p-type. By forming an L shape so as to surround the periphery of the electrode region 15 of the mold side electrode 14, the n type side is also configured to flow more uniformly. As a result, the current flows in a large area and substantially uniformly in the element including the light emitting region (pn junction surface), so that the light emitting area is large and current concentration does not occur substantially.
[0034]
Moreover, also in this embodiment, since the bonding pad 5 and the bonding pad portion 6b are located at the corners on the diagonal of the element, the current flowing in the element becomes more uniform.
[0035]
In addition, in this embodiment as well as the above embodiment, the n-type side electrode 6 is selected so as to have a substantially equal distance from the bonding pad 5 of the p-type side electrode 14, so that the current is more uniform. Turn into.
[0036]
Although it is effective that the n-type electrode is arranged to be less than about half of the p-type side electrode region, the current flow is more uniform if the n-type electrode is provided to be approximately half or more as in the above embodiment. can be it can be achieved in that the at have preferred.
[0037]
In the above description, the n-type layer and the p-type layer are arranged on the substrate. However, the p-type layer and the n-type layer may be arranged on the substrate. In this case, the p-type side, The configuration on the n-type side is opposite to that described above.
[0038]
Of course, the light emitting diode having a single pn junction has been described above, but a double hetero structure or a double hetero structure having an active layer of a quantum well structure may be used.
[0039]
Further, the present invention is not limited to the light emitting diode, but can be appropriately applied to a surface emitting laser or the like.
[0040]
【The invention's effect】
The light emitting device of the present invention includes a substrate and a plurality of semiconductor layers grown on the substrate, and the first electrode for the first conductivity type side and the second electrode for the second conductivity type side on the semiconductor layer side. The first electrode is located substantially over the entire top layer of the first conductivity type among the plurality of semiconductor layers, and the second electrode is located around the top layer. In the light emitting element located on the second conductivity type semiconductor layer of the plurality of semiconductor layers, the second electrode is formed in an L shape around the electrode region of the first electrode, and Since the bonding pad portion is provided at the approximate center of the L-shape, the current flowing in the element has a large area and becomes more uniform, and wire bonding can be made on the same surface side, thereby simplifying bonding.
[0041]
As a result, the light emitting area is large and the device life is extended.
[0042]
The second electrode is positioned on the uppermost layer of the second conductivity type of the plurality of semiconductor layers, and the first conductivity of the plurality of semiconductor layers positioned around the uppermost layer. When located on the semiconductor layer of the mold, it is easy to increase the light emitting area, and wire bonding can be performed on the same surface side, so that bonding is simplified.
[0044]
In addition, when the first electrode is wire-bonded at the corner, and the second electrode is wire-bonded at the bonding pad portion of the second electrode substantially diagonal to the corner Since the distance between the current input / output ports is increased, the current flowing in the element is further increased in area and uniform.
[0045]
Furthermore, when the second electrode is arranged so as to be equidistant from the bonding portion of the first electrode, the current flow can be remarkably made uniform.
[0046]
In particular, a good effect can be obtained even if the second electrode is provided so as to surround approximately half the circumference of the electrode region of the first electrode.
[Brief description of the drawings]
FIG. 1 is a schematic top view of a light emitting diode according to an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view of a light emitting diode according to the embodiment.
FIG. 3 is a schematic top view of a light emitting diode according to another embodiment of the present invention.
FIG. 4 is a schematic top view of a conventional light emitting diode.
FIG. 5 is a schematic cross-sectional view of the conventional light emitting diode.
[Explanation of symbols]
1 Substrate 2 n-type layer 3 p-type layer 6 n-type side electrode 4, 14 p-type side electrode 15 p-type side electrode region

Claims (7)

A substrate and a plurality of semiconductor layers are grown on the substrate, and the first electrode for the first conductivity type side and the second electrode for the second conductivity type side are formed on the same surface side which is the semiconductor layer side. An electrode, wherein the first electrode is located in a substantially entire region on the uppermost layer of the first conductivity type among the plurality of semiconductor layers, and the second electrode is located in a plurality of locations around the uppermost layer. In the light emitting element located on the semiconductor layer of the second conductivity type among the semiconductor layers, the second electrode is formed in an L shape around the electrode region of the first electrode, and the L shape A light-emitting element having a bonding pad portion at substantially the center of the shape .   2. The light emitting device according to claim 1, wherein the first electrode is made of a translucent metal electrode.   3. The light emitting device according to claim 2, wherein the first electrode is a linear metal electrode.   3. The light emitting element according to claim 2, wherein the first electrode is set to a thickness having translucency. The first electrode is wire-bonded at the corner, and the second electrode is wire-bonded at the bonding pad portion of the second electrode substantially diagonal to the corner. The light emitting element according to claim 1, 2, 3, or 4. 6. The light-emitting element according to claim 1, wherein the second electrode is arranged in a shape that is substantially equidistant from the bonding portion of the first electrode. 7. The light emitting device according to claim 1, wherein the second electrode has a substantially half circumference around the electrode region of the first electrode.

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