JP2000077715A - Light-emitting diode array - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dissolve variations in the emissions of light-emitting elements by a method wherein second electrodes are connected with the exposed parts of one conductivity type semiconductor layers under opposite conductivity type semiconductor layers connected with a first electrode, and the second electrodes are connected with the exposed parts at the endmost parts of the one conductivity type semiconductor layers provided in a row form by way of the parts between the insular semiconductor layers. SOLUTION: One conductivity type semiconductor layers 2 and opposite conductivity type semiconductor layers 3 are laminated on the whole surface of a semiconductor substrate 1 or one part of the whole surface of the substrate 1. Thereafter, the layers 2 and 3 are insularly etched and, moreover, the layers 3 are etched in such a way that the side of one end part of each of the layers 2 is exposed to form an exposed part R on each of the layers 2. Different second electrodes 5a and 5b are alternately connected with the exposed parts R in such a way that the electrodes 5a and 5b are extendedly provided from the exposed parts R onto the substrate 1, and a first electrode 4 is formed in such a way that the electrode 4 is extendedly provided from the surfaces of the layers 3 onto the substrate 1 by way of the wall surfaces, which are located on the opposite sides to the electrodes 5a and 5b, of the electrode 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, and more particularly to a light emitting diode array used as an exposure source of a photosensitive drum for a page printer.

[0002]

2. Description of the Related Art FIGS. 4 and 5 show a conventional light emitting diode array. FIG.
FIG. 5 is a sectional view taken along line AA in FIG. 4. 4 and 5, 21 is a semiconductor substrate, 22 is a semiconductor layer of one conductivity type,
23 is a reverse conductivity type semiconductor layer, 24 is a first electrode, and 25 is a second electrode.

[0003] One conductivity type semiconductor layer 22 is formed on a semiconductor substrate 21.
And a reverse conductivity type semiconductor layer 23 having a smaller area than the one conductivity type semiconductor layer 22 is provided on the one conductivity type semiconductor layer 22, and the first electrode 2 is provided on an exposed portion R of the one conductivity type semiconductor layer 22.
4 (24a, 24b) are connected and provided, and the second electrode 25 is connected to the opposite conductivity type semiconductor layer 23. In FIG. 5, reference numeral 26 denotes an insulating film made of a silicon nitride film or the like.

With this configuration, the first electrode 24 and the second electrode 25 can be simultaneously formed on the same side of the semiconductor substrate 21 in one step, so that the manufacturing process of the light emitting diode array is simplified and Also, connection work with an external circuit by a wire bonding method or the like becomes easy.

The first electrodes 24 (24a, 24b)
Is, as shown in FIG. 4, the adjacent one conductivity type semiconductor layer 22.
Are provided in two groups so as to belong to different groups.
The electrodes 25 belong to different groups, and are provided such that adjacent opposite conductivity type semiconductor layers 23 are connected to the same second electrode 25.

In this conventional light emitting diode array, exposed portions R are provided on both sides of a light emitting element row so that opposite end portions of adjacent one conductivity type semiconductor layers 22 are alternately exposed. The first electrode 24 (24a, 24
b), and the second electrode 25 is also connected to the opposite end side for each adjacent opposite conductivity type semiconductor layer 23.

However, if the second electrodes 25 are provided alternately on both ends of the opposite conductivity type semiconductor layer 23, if the mask pattern is misaligned in the process of forming the second electrodes 25, the adjacent electrodes may be adjacent to each other. The area of the light emitting portion of the light emitting element changes,
There is a problem that light emission variation occurs for each light emitting element.

Accordingly, the present inventors have filed a Japanese Patent Application No. Hei 9-1725.
No. 84, as shown in FIG. 6 and FIG.
A plurality of island-shaped one conductivity type semiconductor layers 32 are provided in a row on
The opposite conductivity type semiconductor layer 33 is provided on the one conductivity type semiconductor layer 32 so as to form an exposed portion R on the same end side of the one conductivity type semiconductor layer 32. The same first electrode 35 is connected and provided for each semiconductor layer 33, and the same second electrode 35 is provided on an exposed portion of the one conductivity type semiconductor layer 32 under the opposite conductivity type semiconductor layer 33 to which a different first electrode 35 is connected. A light emitting diode array in which the electrodes 34 (34a, 34b) are connected has been proposed.

As described above, the second electrode 34 (34a, 34b) is connected to the exposed portion R on the same end side, and the first electrode 35 is connected to the same side of the opposite conductivity type semiconductor layer 33. When provided, even if a positional shift occurs in the electrode pattern in the process of forming the first electrode 35, the same positional shift occurs in all the light emitting elements, so that there is no variation in light emission among the light emitting elements. Note that the light emission intensity of the entire light emitting element on the same substrate can be easily adjusted by adjusting the current.

However, in the above-described configuration, as shown in FIG. 8, the wiring at the end is cut along the line BB to form the second electrode 34 (34c) having an island shape in an external circuit. In addition, as shown in FIG. 9, only the outermost one-conductive-type semiconductor layer 32a forms an exposed portion R on the opposite end side of the light-emitting element row, and connects the second electrode 34b. Along with
The first electrode 35 is connected to the opposite side of the opposite conductivity type semiconductor layer 33, but in the former case, it is difficult to connect to an external circuit, and in the latter case, only the light emitting element at the end is misaligned. The light-emitting device has a drawback that it causes uneven light emission and that only the light-emitting element at the end has a different light-emitting intensity distribution in the element, thereby causing uneven printing.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and eliminates variations in light emission of light emitting elements due to misalignment of electrode patterns in all light emitting elements. An object of the present invention is to provide a light emitting diode array capable of making the distribution uniform.

[0012]

In order to achieve the above object, in the light emitting diode array of the present invention, a plurality of island-shaped semiconductor layers of one conductivity type are provided on a substrate, and the plurality of islands of one conductivity type are provided. The opposite conductivity type semiconductor layer is provided on the one conductivity type semiconductor layer so as to form an exposed portion on the same end side of the semiconductor layer, and the same first conductivity type semiconductor layer is provided for each of the adjacent opposite conductivity type semiconductor layers.
A light emitting diode array in which the same second electrode is connected to an exposed portion of the one conductivity type semiconductor layer below the opposite conductivity type semiconductor layer to which a different first electrode is connected. Wherein the second electrode is connected to the exposed end portion provided in the row via the island-shaped semiconductor layers.

[0013]

With the above construction, since all the exposed portions are arranged in the same manner, there is no variation in the light emission of the light emitting elements due to the displacement of the electrode pattern, and the light emission intensity distribution is the same for all the light emitting elements. The printing quality is improved.

[0014]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. 1 and 2 are views showing one embodiment of a light emitting diode array according to the present invention, and FIG. 3 is a cross-sectional view taken along line AA in FIG. 1, 2 and 3, 1 is a substrate, 2 is a semiconductor layer of one conductivity type, 3 is a semiconductor layer of opposite conductivity type, 4 is a first electrode, and 5 (5a, 5b).
Is a second electrode.

The substrate 1 is made of, for example, a single crystal semiconductor substrate such as silicon (Si) or gallium arsenide (GaAs) or a single crystal insulating substrate such as sapphire (Al ₂ O ₃ ). Even when a semiconductor substrate is used as the substrate 1, it is desirable to use a semiconductor substrate having as high a resistance as possible. In the case of a single crystal semiconductor substrate, a (100) plane or the like is used, and in the case of sapphire, a C plane or the like is used.

The one conductivity-type semiconductor layer 2 is made of a multilayer film of gallium arsenide or gallium arsenide and aluminum gallium arsenide, for example, silicon or selenium (Se) one conductivity type semiconductor impurity l × 10 ¹⁶ ~10 ¹⁹ atom, such as / Cm ³
Content. This one conductivity type semiconductor layer 2 is formed, for example, of MO
It is formed by a CVD method, an MBE method, or the like. That is, when the semiconductor substrate is used as the substrate 1 and formed by the MOCVD method, a natural oxide film of the semiconductor substrate is removed at a high temperature of 800 to 1000 ° C., and then an amorphous gallium arsenide film serving as a nucleus at a low temperature of 450 ° C. or less is formed. After growing to a thickness of about 0.1 to 2 μm, the temperature is raised to 500 to 700 ° C. and recrystallized to grow a gallium arsenide single crystal (two-step growth method).
In this case, trimethyl gallium ((CH ₃ ) ₃ Ga) or the like is used as a raw material of gallium, and arsine (AsH ₃ ) or the like is used as a raw material of arsenic. Next, 7
Post annealing such as repeating annealing at a high temperature of 50 to 1000 ° C. and rapid cooling to a low temperature of 600 ° C. or less several times (temperature cycle method) is performed. In the case of a two-layer structure of gallium arsenide and aluminum arsenide, an aluminum gallium arsenide layer is further formed. As a raw material of aluminum, trimethyl aluminum ((CH ₃ ) ₃ Al) or the like is used.

On the one conductivity type semiconductor layer 2, a reverse conductivity type semiconductor layer 3 is formed. The opposite conductivity type semiconductor layer 3 is also made of a compound semiconductor such as aluminum gallium arsenide (AlGaAs), and contains 1 × 10 ¹⁸ to 10 ¹⁹ atoms of opposite conductivity type semiconductor impurities such as zinc (Zn) and strontium (Sr).
/ Cm ³ . A semiconductor junction is formed at the interface between the one conductivity type semiconductor layer 2 and the opposite conductivity type semiconductor layer 3. The one conductivity type semiconductor layer 2 and the opposite conductivity type semiconductor layer 3 are formed in an island shape. The opposite conductivity type semiconductor layer 3 may be formed of a plurality of layers having different compound crystal ratios.

After laminating the one conductivity type semiconductor layer 2 and the opposite conductivity type semiconductor layer 3 on the entire surface or a part of the substrate 1, the one conductivity type semiconductor layer 2 and the opposite conductivity type semiconductor layer 3 are formed into an island shape. Etching is performed, and then the opposite-conductivity-type semiconductor layer 3 is etched so that one end of the one-conductivity-type semiconductor layer 2 is exposed to form an exposed portion R in the one-conductivity-type semiconductor layer 2.

The island-shaped one-conductivity-type semiconductor layer 2 and the opposite-conductivity-type semiconductor layer 3 are covered with a protective film 6 made of, for example, a silicon nitride film. 1 to extend over, for example, gold (Au)
The second electrodes 5a and 5b are formed. One-conductivity-type semiconductor layer 2 includes second electrodes 5a that are alternately different from each other.
5b are connected alternately. That is, the one-conductivity-type semiconductor layer 2 is divided into two groups and different second electrodes 5a, 5b
Connected to.

The second surface of the opposite conductivity type semiconductor layer 3
The first electrode 4 is formed so as to extend on the semiconductor substrate 1 via the wall surface opposite to the electrode 5. That is, the first electrode 4 is connected and provided for each light emitting diode belonging to a different group. The wide portion of the first electrode 4 becomes a terminal portion for connecting to an external circuit by wire bonding or the like. By selecting a combination of the second electrodes 5a and 5b and the first electrode 4, individual light emitting diodes can be selected to emit light.

In the light emitting diode array according to the present invention,
An exposed portion R is provided so that the same end portion of the one conductivity type semiconductor layer 2 is exposed, and the second electrode 5a, 5b is connected to the exposed portion R and provided opposite to the opposite conductivity type semiconductor layer 3. A first electrode 4 is connected and provided on the end side, and first electrodes 4a and 4b are connected and arranged on the extreme end so as to correspond to individual light emitting elements. The second electrode 5c is provided so as to be connected to the exposed portion R via a space. When connecting to an external circuit, the first electrodes 4a, 4b
Are connected to the same terminal, it is possible to operate the extreme end in the same manner as other light emitting elements.

As described above, the second exposed portion R on the same end portion is
And the first electrode 4 is connected to the same end of the opposite conductivity type semiconductor layer 3 and the second electrode 5c is connected to the other end of the semiconductor layer 3 at one end. When the first electrodes 4a and 4b are individually connected to the opposite conductivity type semiconductor layer 3, the first electrodes 4 and 4a are connected to each other. Even if a displacement occurs in the electrode pattern in the process of forming 4b, the same displacement occurs in all the light emitting elements, so that there is no variation in light emission among the light emitting elements. Therefore, the light emission intensity distribution of all the light emitting elements becomes the same. The light emission intensity of the light emitting element can be easily adjusted by adjusting the current,
The intensity of the light emission intensity of the entire light emitting element on the same substrate can be easily adjusted.

According to this embodiment, if the one conductivity type semiconductor layer 2 is n-type and the opposite conductivity type semiconductor layer 3 is p-type, the space between the opposite conductivity type semiconductor layer 3 and the one conductivity type semiconductor layer 2 is provided. When a current flows in the forward direction, if the other second electrode 5b is connected while one second electrode 5a is open, only the light emitting diode connected to the other second electrode 5b emits light. I do. Therefore, even if the common first electrode 4 is provided for each of the adjacent opposite conductivity type semiconductor layers 3, the second electrodes 5a, 5b
Are connected separately, the second electrode 5
By changing the connection state between a and 5b and the first electrode 4, it becomes possible to selectively cause adjacent light emitting diodes to emit light. The first electrodes 4a, 4b also at the end portions
Are connected to the same external circuit. Therefore, when a current flows between the opposite conductivity type semiconductor layer 3 and the one conductivity type semiconductor layer 2 in the forward direction, one second electrode 5a is opened. When the other second electrode 5b is connected, only the light emitting diode connected to the first electrode 4b emits light.

[0024]

As described above, according to the light-emitting diode array according to the present invention, the exposed portions of the plurality of one-conductivity-type semiconductor layers are provided on the same side of the light-emitting element row, and the exposed end of the row is exposed. Since the second electrode is connected to the portion via the island-shaped semiconductor layer, even if the electrode pattern is displaced, it is possible to minimize the occurrence of light emission variation in the light emitting element.
Further, by arranging all the light emitting elements equally, it is possible to make the light emission intensity distribution uniform for all the light emitting elements and to improve the printing quality.

Further, even if a slight displacement occurs in the electrode pattern, there is no variation in light emission in the light emitting element. Therefore, the mask pattern can be aligned in the formation of the electrode in a short time, and the manufacturing can be simplified. It will be easier.

[Brief description of the drawings]

FIG. 1 is a plan view showing one end side of a light emitting diode array according to the present invention.

FIG. 2 is a plan view showing another end of the light emitting diode array according to the present invention.

FIG. 3 is a sectional view showing a light emitting diode array according to the present invention.

FIG. 4 is a plan view showing a conventional light emitting diode array.

FIG. 5 is a sectional view taken along line AA of FIG. 4;

FIG. 6 is a plan view showing one end side of another conventional light emitting diode array.

FIG. 7 is a sectional view taken along line AA of FIG. 6;

FIG. 8 is a plan view showing another end portion of another conventional light emitting diode array.

FIG. 9 is a plan view showing another end portion obtained by improving another conventional light emitting diode array.

[Explanation of symbols]

1 substrate, 2 semiconductor layer of one conductivity type, 3 semiconductor layer of opposite conductivity type, 4 first electrode, 5 (5a, 5
b) {Second electrode, R} exposed part

Claims (1)

[Claims] A plurality of island-shaped one-conductivity-type semiconductor layers are provided in a row on a substrate, and the one-conductivity-type semiconductor layers are formed such that exposed portions are formed on the same end side of the plurality of one-conductivity-type semiconductor layers. A reverse conductivity type semiconductor layer is provided by laminating a reverse conductivity type semiconductor layer on a semiconductor layer, and the same first electrode is connected and provided for each adjacent reverse conductivity type semiconductor layer, and a different first electrode is connected. In a light-emitting diode array in which the same second electrode is connected to an exposed portion of the one-conductivity-type semiconductor layer below the layer, the second electrode is provided at an exposed portion at the end provided in the row. A light emitting diode array connected between the island-shaped semiconductor layers.