JPH07202259A - Gaalas light emitting diode - Google Patents

Abstract

PURPOSE:To make an output uniform with high output by employing advantages of both a peripheral electrode type and a central electrode type. CONSTITUTION:An n-type side metal electrode 2 is outputted from one side of a light emitting region 1, and connected to a wiring 4. In order to take preferably ohmic connection to the electrode 2, a contact layer 3 for the electrode is formed on the electrode. The layer 3 has a low resistance, is formed of an n-type GaAlAs layer having low Al mixed crystal ratio, and further extended along a center of a light emitting region 5mum from the contact with the electrode 2 of a peripheral electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a GaAlAs light emitting diode, and more particularly to a light emitting diode suitable for a fine structure.

[0002]

2. Description of the Related Art Conventionally, a light emitting diode having a fine structure such as a light emitting diode array has a peripheral electrode type in which an electrode 2 is provided in the peripheral portion of a light extraction region 1 as shown in FIG. As shown in FIG. 6, there are two types of center electrode type in which an electrode 2 is provided at the center of the light extraction region 1. In each case, the electrode 2 is extracted on the light extraction region 1 through the electrode contact layer 3, and the electrode 2 is connected to the wiring 4.

[0003]

However, in the peripheral electrode type light emitting diode shown in FIG. 5, since the electrode 2 is in the peripheral portion of the light extraction region 1, the injected current can be spread evenly over the entire light extraction region. Will be very difficult. As a result, the output of the extracted light decreases in a region farther from the electrode 2, so that the light output in the light extraction region 1 becomes non-uniform and a high output cannot be output.

On the other hand, in the center electrode type light emitting diode shown in FIG. 6, since the electrode 2 is located at the center of the light extraction region 1, the drawbacks of the peripheral electrode type light emitting diode can be covered.
However, in the case of a fine structure, it becomes difficult to obtain a high-power light emitting diode due to an increase in the coverage of the electrode in the light extraction region, and a problem also occurs in the shape of the light emission spot.

The object of the present invention is to solve the above-mentioned drawbacks of the prior art by utilizing the advantages of both the peripheral electrode type and the center electrode type by utilizing the electrode contact layer, and to achieve high output and uniform output. Another object is to provide a GaAlAs-based light emitting diode.

[0006]

According to the present invention, in a peripheral electrode type GaAlAs light emitting diode in which an electrode is provided around a light extraction region via a contact layer, the present invention is located around the light extraction region provided with an electrode. The contact layer is drawn out from the periphery of the light extraction region to approximately the center of the light extraction region.

Further, the present invention is a peripheral electrode type GaA in which electrodes are provided on opposite sides of the light extraction region via a contact layer.
In the 1As-based light emitting diode, a contact layer located on the opposite side of a light extraction region provided with an electrode is connected across substantially the center of the light extraction region.

The contact layer is made of AlGaA.
It is formed of a compound semiconductor crystal such as s or GaAs.

[0009]

When an electrode contact layer made of a GaAlAs layer having a low resistance and a low mixed crystal ratio is drawn out from the periphery of the light extraction region to approximately the center or across the center of the light extraction region, the electrode provided around Since the GaAlAs contact layer greatly contributes to the spread of the injection current in the light emitting region, the light output in the light extraction region can be made uniform and the light output can be greatly improved.

[0010]

1 to 3 show a peripheral electrode type light emitting diode for explaining an embodiment of the present invention. The structure of this light-emitting diode is a GaAlAs-based light-emitting diode having a fine size and having a single hetero structure with separated mesas.

FIG. 1 is a plan view. The light extraction region 1 is designed as a very fine light emitting diode with a horizontal width X of 25 μm and a vertical width Y of 25 μm. The n-side metal electrode 2 is provided on one side (lower side in the illustrated example) in the light extraction region 1 and is made of Al.
Is connected to the metal wiring 4.

In order to obtain a good ohmic contact with the electrode 2, an electrode contact layer 3 is formed under the electrode.
The electrode contact layer 3 is composed of an n-type GaAlAs layer having a low resistance and a low Al mixed crystal ratio, and has a width of 5 μm from the contact portion with the n-side electrode 2 which is a peripheral electrode. Stretched along the center of. The contact layer is preferably light transmissive,
It need not be light transmissive. Further, low resistance GaAs may be used as the contact layer.

In the illustrated example, the extended electrode contact layer 3 is linear, but one may be extended, and the electrode contact layer 3 is not limited to linear.

FIG. 2 is a sectional view in which the light emitting diode chip is cleaved along the line AA shown in FIG. 1, and FIG.
FIG. 4 is a sectional view of the light emitting diode chip cleaved along the line BB.

On the p-type GaAs substrate 8, a p-type GaAlAs layer 7 which becomes an active layer and an n-type G having a high mixed crystal ratio which becomes a clad layer are formed.
The aAlAs layer 6 is formed. As described above, the pn layer has a single hetero structure and a mesa separation type structure. On the n-type GaAlAs layer 6, a contact layer 3 made of a GaAlAs layer having a low resistance by being highly doped to form an electrode contact layer and having a low Al mixed crystal ratio, and further, a protective glass film 5 on the surface, The wiring 4 connected to the electrode 4 and the p-side electrode 9 are attached to the back surface.

When the light emitting diode shown in FIGS. 1 to 3 is energized, there is an n-type AlGaAs layer which is a contact layer 3 extended along the center of the light extraction region 1 in spite of the peripheral electrode structure. Therefore, this n-type Ga
The injection current spreads through the AlAs layer into the light emitting region formed near the pn interface. Therefore, the light output can be made uniform in the light extraction region 1, and at the same time, high output can be achieved.

Actually, when the conventional peripheral electrode type light emitting diode shown in FIG. 5 was trial-produced in the same size as the peripheral electrode type light emitting diode of this embodiment and the light outputs were compared, the light emitting diode of this embodiment was , About 1.4 of the light emitting diode of FIG.
Double light output was obtained. Similarly, a light output about 15% higher than that of the center electrode type light emitting diode shown in FIG. 6 was obtained.

As described above, according to this embodiment, the metal electrode is provided around the light extraction region as in the conventional case, and the low resistance semiconductor electrode is provided at the center instead of the metal electrode. Unlike the center electrode type, the electrode coverage in the light extraction region does not increase, so that high output can be easily achieved and the shape of the light emission spot does not cause any inconvenience. Further, if the GaAlAs contact layer led out in the center is made light-transmissive, a higher light output can be obtained than that of the center electrode type light emitting diode that shields the light in the central portion. As a result, it can be applied to a light emitting diode array or the like that requires a higher density light source.

FIG. 4 shows a modification of the present invention. The n-side electrodes 2 which are commonly connected to the wiring 4 are provided on the upper and lower opposing sides in the light emitting region, and the center of the light extraction region 1 is crossed between the electrode contact layers 3 below the opposing electrode 2. It is a bridge type light emitting diode connected by a contact layer 3 made of a GaAlAs layer having a low resistance and a low mixed crystal ratio. In this case as well, the number of the electrode contact layers that traverse is linear, but a plurality of electrode contact layers may be extended, and the number of electrode contact layers is not limited to linear. The counter electrodes are not limited to the upper and lower sides, but may be on the left and right sides or on the adjacent sides.

This light emitting diode, when compared with the light emitting diode shown in FIG. 1, has a drawback that the coverage of the electrodes in the light emitting region increases when the light emitting diode has a fine structure. However, in the case of a comparatively large light emitting diode whose width of the light emitting region exceeds several tens of μm, the effect of increasing the output and making the light output in the light extraction region uniform is greater than that of the light emitting diode of FIG.

[0021]

【The invention's effect】

(1) According to the GaAlAs-based light emitting diode of claim 1, since the contact layer is drawn out substantially in the center of the light emitting region to diffuse the injected current, the output is higher than that of the conventional peripheral electrode type light emitting diode. It is possible to make the light output and the light output in the light extraction region uniform.

(2) According to the GaAlAs-based light-emitting diode of the second aspect, the contact layer is connected to the contact layer under the electrode facing across the substantially center of the light extraction region, so that the output is further increased. Also, the light output in the light extraction region can be made uniform.

[Brief description of drawings]

FIG. 1 is a plan view of a peripheral electrode type light emitting diode for explaining an embodiment of a GaAlAs-based light emitting diode of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG.

FIG. 4 is a plan view of a peripheral electrode type light emitting diode for explaining a modification of the present invention.

FIG. 5 is a plan view of a conventional peripheral electrode type light emitting diode.

FIG. 6 is a plan view of a conventional center electrode type light emitting diode.

[Explanation of symbols]

1 Light extraction region 2 n-side electrode 3 Contact layer for electrode (low resistance, low Al mixed crystal ratio GaA
1As layer) 4 Wiring 5 Glass film 6 n-type GaAlAs layer (cladding layer) 7 p-type GaAlAs layer (active layer) 8 p-type GaAs substrate 9 p-side electrode

Claims (2)

[Claims] 1. A peripheral electrode type GaAlAs-based light-emitting diode in which an electrode is provided around a light extraction region via a contact layer, wherein a contact layer located around the light extraction region in which the electrode is provided is the light extraction region. A GaAlAs-based light-emitting diode, characterized in that the light is extracted from the periphery of the region to approximately the center of the light extraction region. 2. In a peripheral electrode type GaAlAs light emitting diode having electrodes provided on the opposite sides of the light extraction region via a contact layer, the contact layers located on the opposite sides of the light extraction region provided with the electrodes are the light extraction regions. A GaAlAs-based light-emitting diode, which is connected across substantially the center of the region.