JPH0613656A - Light emitting diode array - Google Patents

Abstract

PURPOSE:To provide a light emitting diode array of high resolution by making luminance characteristic in an alignment direction of a light emitting region uniform. CONSTITUTION:A plurality of light emitting regions 4 are formed on a surface of a compound semiconductor 1 and an insulation layer 2 is formed on a surface of the compound semiconductor 1 to expose the light emitting region 4. The light emitting region 4 is divided into about two and a surface electrode 5 is formed close to a center of the light emitting region 4 in a stripe with one end in ohmic contact and the other end positioned on the insulation layer 2. A stripe electrode 8 having approximately the same width as the front electrode 5 on the light emitting region 4 is formed on the insulation layer 2 between adjacent light emitting regions 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting diode array used in an optical printer head.

[0002]

2. Description of the Related Art In recent years, a light emitting diode array in which light emitting regions are formed with high density by a selective diffusion method is disclosed in JP-A-60-66.
No. 273, etc. FIG. 3 showing this publication
At this point, a plurality of light emitting regions 22 are formed on the surface of the compound semiconductor 21. An insulating layer 23 is formed on the compound semiconductor 21 so as to expose the light emitting region 22. A surface electrode 24 is formed in ohmic contact in a stripe shape at approximately the center of the light emitting region 22.

[0003]

However, in such a light emitting diode array, the luminance characteristics in the alignment direction of the light emitting regions 22 are as shown in 25 of FIG. Is reduced. The reason for this is that the area between adjacent light emitting areas 22 is a non-light emitting area, and the brightness is extremely reduced at the position 26 corresponding to that area.
Due to this non-uniform brightness characteristic, high resolution cannot be obtained.
Therefore, the present invention has been made in view of the above-mentioned drawbacks of the conventional array, and provides a high resolution light emitting diode array by uniformizing the brightness characteristics in the alignment direction of the light emitting regions. .

[0004]

In order to solve the above problems, the present invention forms a plurality of light emitting regions on the surface of a compound semiconductor and forms an insulating layer on the surface of the compound semiconductor so as to expose the light emitting regions. Form. The light emitting region is divided into two approximately equal parts, and one end is ohmic-contacted in a stripe shape at substantially the center of the light emitting region,
A surface electrode is formed so that the other end is located on the insulating layer. Then, a stripe electrode is formed on the insulating layer having the same width as the surface electrode on the light emitting region and between the adjacent light emitting regions.

[0005]

According to the present invention, as described above, the stripe electrode is formed on the insulating layer having the same width as the surface electrode on the light emitting region and between the adjacent light emitting regions. Therefore, the light emitted from the light emitting region is reflected by the stripe electrode and travels upward, so that the decrease in luminance in the non-light emitting region is reduced.

[0006]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a sectional view of a main part of a light emitting diode array according to this embodiment, and FIG. 2 is a plan view of a main part of the light emitting diode array. In these figures, the compound semiconductor 1 is obtained by vapor phase epitaxial growth of an n-GaAsP layer on a GaAs base, for example. The insulating layer 2 is provided on the surface of the compound semiconductor 1 and is made of a silicon nitride (Si ₃ N ₄ ) film or the like by the CVD method. Insulating layer 2 is compound semiconductor 1
A plurality of through holes 3 are formed at predetermined intervals along the longitudinal direction of the.

The light emitting region 4 is a P type diffusion region formed on the surface of the compound semiconductor 1 by selective diffusion of zinc using the insulating layer 2 as a mask, and a Pn junction is formed at the boundary thereof. For example, in order to manufacture a light emitting diode array of 400 dpi, the light emitting regions 4 may be formed to have a length of 46 μm, a width of 50 μm, and an interval of 63.5 μm along the longitudinal direction of the compound semiconductor 1.

The surface electrode 5 has an ohmic contact portion 6 which is in ohmic contact with the light emitting region 4 at one end and a wiring portion 7 which is located on the insulating layer 2 at the other end, and is made of an aluminum vapor deposition film or the like. The ohmic contact portion 6 is substantially orthogonal to the alignment direction of the light emitting regions 4 and divides the light emitting regions 4 into two substantially equal parts.
Is located approximately at the center, its width is 10 to 15 μm, and its thickness is 1 to 5 μm. The wiring portion 7 is formed wider than the ohmic contact portion 6 to facilitate wire bonding.

The stripe electrode 8 is formed on the non-light emitting area of the insulating layer 2 located between the adjacent light emitting areas 4 by vapor deposition of aluminum or the like. The width of the striped electrode 8 is set to 10 to 15 μm, which is substantially the same as the width of the ohmic contact portion 6, and the thickness thereof is set to 1 to 5 μm. The side surfaces of both the striped electrode 8 and the ohmic contact portion 6 are inclined so that the cross section has a substantially trapezoidal shape. The back surface electrode 9 is formed on the back surface of the compound semiconductor 1 and has a function as a common electrode.

The reflected light 10 is the light which is emitted from the light emitting region 4 and then reflected by the inclined side surface of the ohmic contact portion 6 to travel upward. The reflected light 11 is light that is reflected by the inclined side surface of the stripe electrode 8 on the insulating layer 2, which is a non-light emitting area, after the light emitting area 4 and travels upward.

Next, the luminance characteristic in the alignment direction of the light emitting diode array according to the present embodiment is shown at 12 in FIG. In this figure, the brightness lowering portion 13 corresponds to the ohmic contact portion 6, and the brightness lowering portion 14 corresponds to the stripe electrode 8.
It can be seen that the present invention causes an extremely small decrease in luminance on the non-light emitting area as compared with the conventional art. This is the stripe electrode 8 of the present invention.
This is because the light reflected by the side surface of the light reduces the decrease in brightness on the non-light emitting area.

[0012]

As described above, the present invention forms the stripe electrode on the insulating layer between the adjacent light emitting regions. Therefore, the light emitted from the light emitting region is reflected by the stripe electrode and travels upward, so that the decrease in luminance in the non-light emitting region is reduced. Further, the surface electrode on the light emitting region, that is, the width of the ohmic contact portion and the width of the stripe electrode are formed substantially the same. Therefore, by setting the brightness of the reflected light by the ohmic contact portion and the brightness of the reflected light by the stripe electrode to be substantially the same, the decrease in brightness on the stripe electrode can be made substantially the same as the decrease in brightness on the ohmic contact part. As a result, the brightness in the alignment direction of the light emitting regions is made uniform. Since the ohmic contact portion is provided substantially in the center of the light emitting region, the luminance characteristic is symmetrical with respect to the ohmic contact portion. Therefore, since the luminance characteristic on the ohmic contact portion and the luminance characteristic on the stripe electrode are substantially the same, the resolution is doubled,
A high resolution light emitting diode array is obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a light emitting diode array according to an embodiment of the present invention.

FIG. 2 is a plan view of an essential part of a light emitting diode array according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view of a conventional light emitting diode array.

FIG. 4 is a luminance characteristic diagram in the alignment direction of the light emitting diode array.

[Explanation of symbols]

 1 Compound Semiconductor 2 Insulating Layer 4 Light Emitting Area 5 Surface Electrode 8 Stripe Electrode

Claims (1)

[Claims] 1. A plurality of light emitting regions formed on the surface of a compound semiconductor, an insulating layer formed on the surface of the compound semiconductor so as to expose the light emitting regions, and the light emitting region are divided into two substantially equal parts. Between the surface electrode formed on the insulating layer in ohmic contact in a stripe shape substantially in the center of the light emitting region and the adjacent light emitting region having substantially the same width as the surface electrode on the light emitting region. And a stripe electrode formed on the insulating layer.