JPS6188575A - LED array - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an LED array as a modulated light source used as a light source for irradiating a photosensitive drum of an optical printer.

[Prior Art] Conventionally, L[D arrays used in optical printers and the like have been of the so-called plane light emitting type. That is, a mixed crystal epitaxial layer of -x x such as GaAs P is grown on a single crystal substrate such as GaAs, and this epitaxial growth 1? The structure was such that the light emitted from the injection type light emitting region formed in g was extracted from the surface of the epitaxy 1 full growth layer.

However, a planar light emitting type LED array usually requires about 8 light emitting parts per 1M width, and at least 4 or more light emitting parts, so the Wr structure of the ohmic electrode provided directly above the light emitting part becomes fine and the light emitting area is small. It is also necessary to increase the mixed crystal ratio of the epitaxial cell growth layer (1) to provide optical transparency, and it is necessary to form an A-mic contact with sufficiently low contact resistance in the solid layer (1).

Therefore, it has not been easy to produce devices with a stable high yield. However, if a large metal electrode is formed on the surface of the element where the light-emitting part is provided, this electrode will prevent light emission, and if a small electrode is formed, each electrode formed in each light-emitting part will The difference in contact resistance becomes large, and the light emission intensity of each light emitting part tends to become non-uniform.

In addition, in order to lower the contact resistance by 4 minutes, the mixed crystal ratio is lowered by narrowing the energy forbidden band width on the surface of the mixed crystal epitaxial growth layer in contact with the electrode, and this narrow band gap layer absorbs light. However, the efficiency of emitting light to the outside was still reduced.

For this reason, in the conventional planar light emitting type LED array, the impurity is 7 cubic centimeters from the surface of the n-type epitaxial growth layer. By selectively diffusing Zn, rows of fine p-type regions (i.e., light-emitting regions) are created, and each p-type region is
- The idea was to form separate microelectrodes on the surface of the mold region. In this way, Zr+Kr1
The surface of the l region (i.e. the light emitting part) is at least 1102
Since the carrier concentration is as high as 0 C゛3, the contact resistance with the electrode is low, but there is still a problem in that the high carrier concentration increases light absorption in the Zn diffusion region.

[Purpose of R-light] In view of the problems of the prior art described above, the present invention provides an LED array in which the electrodes formed in each light-emitting region have body contact resistance and the light emission is not hindered by these electrodes. The purpose is to provide.

[Means for solving the problem] In the LED array of the present invention, the light emitting part is formed on the side surface of the element with a width of 1
The elements are formed at a ratio of 4 points per mm, and are characterized in that ohmic electrodes are formed on the surface of the element.

"Example code" Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

Example 1 FIG. 1 is an explanatory diagram that does not show one embodiment of the present invention.

An n-type Ga Af-X XAS layer 2 is formed on the surface of the n-type GaAs4 plate 1. An n-type Ga AIVAS layer 3 and a -yn1-type GaAS layer 4 are sequentially grown. Next, n1
A phospho-A silicate glass (PSG) film 5 is formed on the surface of the type GaAS layer 4, and the PSGSbO2 portion is removed in a semicircular manner at appropriately set intervals, so that n1 is formed in the PSGSbO2 removed portion. type GaAS layer 4
Negative electrodes (
Ohmic electric t! V holes 6 are formed in an array on the PSGSbO2, and a semicircular ohmic contact portion 7 is formed.

Then, a semicircular depression 6a is formed in the portion of the negative electrode 6 that is in contact with the nj-type GaAS layer exposed by removing the PSGSbO2. A positive electrode (ohmic electrode) 8 is formed on the entire back surface of the p-type GaAS substrate 1 .

In an element having such a configuration, when a voltage is biased in the forward direction between the negative electrode 6 and the positive electrodes 8J and 8,
The current flows concentratedly in each of the ohmic contacts 7,
Light is emitted laterally from the light emitting section 9 on the side surface of the element.

That is, the n1 type GaAS layer 4 has PSGS on its surface.
The ohmic contacts 7 with low contact resistance are formed by inserting the bO2 into each of the negative electrode contacts 6 which are separated from each other and provided in an array. n-type Ga via XAS layer 3
AI! It is injected into -X of XASIiIf 72 by 8 degrees, undergoes radiative recombination with holes inside the light emitting part, and light is emitted from the light emitting part 9 on the side surface of the element.

The number of ohmic contact portions 7 and the structure of the negative electrode 6 are the same, but for LEI (LEI) arrays for printers, it is necessary to form ohmic contact portions 7 at four or more locations per 1 mm width of the element. Ohmic contact portions 7 are usually formed at 8 locations, but in some cases at 16 locations. Note that if the radius of curvature of the ohmic contact part 7 is set to about 1 m or less, the injection type light emission within the n-type Ga1-xAirxAsFj2 will be emitted laterally from the light-emitting part 9 without being absorbed much within the same layer. Ru.

Furthermore, the n1-type GaAS layer 4 does not transmit resident-type light emission and has no effect on light emission from the side of the device. It is possible to reduce the area of the light emitting section 9 to 1.

Example 2 FIG. 2 is an explanatory diagram showing another embodiment of the present invention.

As in Example 1, n-type G is deposited on the surface of p-type QaΔS substrate 1.
a Af! xAsE'42. n-type Ga t＼1
-X 1-YJyAstn3
Then, an nt-type GaAS layer 4 is successively grown.

In the case of this embodiment, the current is
In order to prevent the light from entering the NT-type GaAS layer 4 and to increase the current density at the ohmic contact part 7 to increase the light emission energy, the light emitting part 9 is formed at a depth that penetrates the NT-type GaAS layer 4 so as not to pass through the ohmic contact part 7. Parallel etchings 10 are provided on the sides of the cord. Then on top of this PS
After the G film 5 is formed and a part of the PSG film 5 is removed in a semicircular shape, the negative city poles 6 are formed in an array so as to contact the n1 type GaAS layer 4 and form an ohmic contact part 7. It is formed. A positive electrode 8 is formed on the back surface of the p-type GaAS substrate 1 as in the first embodiment.

Therefore, when a voltage is biased in the forward direction between the minus 7fi pole 6 and the plus electrode 8, the current flows in the n1 type GaAS
The light flows through the ohmic contact portion 7 in a concentrated manner without being diffused throughout the layer 4, and is emitted laterally from the light emitting portion 9 Q4.

Further, as shown in FIG. 3, by providing a second etching groove 11 perpendicular to the etching groove 10 and having a depth penetrating the n-type GaAS layer 4 between each light emitting part 9, the current can be reduced. Diffusion in the direction parallel to the side surface of the element having the light emitting portion 9 in the n-type QaAS layer 4 can be prevented.

Therefore, the current is concentrated on the ohmic contact portion 7, and the light emission energy can be increased.

Note that only the PSG film 5 is formed on the surface of the second etching groove 11.

Embodiment 3 FIG. 4 is an explanatory diagram showing another embodiment of the present invention.

On the n-type GaAS substrate, there is an n-type Ga 1-X A I
i XAs layer 12. p'! jlGa1-y Affl
A yAs layer 13 and an n1 type GaAS layer 14 are sequentially grown. Next, zn is selectively diffused at an appropriately set distance of 1 m from the surface of the n-type GaAS layer 14, and the p-type diffusion region 2
2 is formed. This p-type diffusion region 22t is composed of n-type Ga
1-XAJXAS layer 12.

Next, a p-type extended region 22 is formed on the surface of the n-type GaAS layer 14.
An L-shaped negative electrode 16 is formed at one end of the P
After the SG film 15 is formed continuously in the horizontal direction in the figure, the p-type diffusion region [2] where the negative electrode 16 is not formed is formed.
A negative electrode 26 is formed on top of PSGil 5 to contact PSGil 2 .

By using such a two-stage negative electrode,
The electrode area can be increased and wire bonding can be facilitated.

Furthermore, the p-type diffusion region 22 with which the negative 71Hffi 16 and 26 are in contact not only has a high carrier temperature and can easily lower the contact resistance, but also has a high carrier temperature.
The concentration of the electron flow from the positive electrode 8 formed on the back surface of the p-type diffusion region 22 is also improved, and injection light emission occurs directly under the p-type diffusion region 22, and light is emitted from one light-emitting portion.

Moreover, if multilayer wiring is used through such an insulating film,
It is also possible to wire the negative electrodes in three or more stages over a wider area.

In addition, in the case of d5, Ga is used as a plate crystal.
Although the description has been made using As and GaAfAS as the epitaxial layer, it is also possible to implement the present invention using other semiconductor materials.

Also, a method for forming a p-n junction and a heterojunction, or
The present invention can be implemented using methods other than the above-mentioned embodiments, such as the method for forming the radiative recombination region formed by these methods. Any device may be used as long as it emits light from the side surface of the element on which no surface is formed.

[Efficacy of invention! l! 1. As explained above, the LED array of the present invention provides the following remarkable effects.

(1) Since the light emitting part is on the side of the element, light emission is not obstructed by electrodes, and LEDs with high light emission density do not require windows for light extraction in the electrodes and ohmic contact layer.
1 array! I can.

(2) Since light can be extracted from the side of the device where there is no highly doped narrow energy bandgap layer that easily forms electrodes and ohmic contacts, there is a large degree of freedom in the design of current and A-mic contact layers. , it is possible to form electrodes with low contact resistance.

(3) Since the electrode formation process and the light emitting part formation process are unrelated, the electrode formation process is less likely to cause non-uniformity in the light emission intensity of a large number of light emission points, and the LED array can be manufactured with high yield. I can do it.

(4) Since the light emitting part is minute, light absorption is low even though the light is emitted from the side of the device.

[Brief explanation of the drawing]

FIG. 1 shows wave distortion. FIG. 4 is an explanatory diagram showing an embodiment of the present invention. 1...p-type GaAS substrate. 2...O-type G a 1-X A flX A S layer. 3-1yAs layer on n-type Ga1-yA. 4.14 n' type GaAS) ffl. 5.15...PSG film. 6.16.26... Negative electrode. 7... Ohmic contact part, 8... Positive electrode. 9.19... Light emitting part. 10... (first) etching groove. 11...Second etching groove. 12-n-type Ga1. 1XAS layer on A. 13 ・D-type Ga Af VAs layer. -Y 21 ・N-type GaAs1 plate. 22...p-type diffusion area garden 1121 7; Omi, 711 tsubo 8 near 4 lightning strikes 4, 1 light emitting light 2 mouths

Claims (1)

[Claims] (1) At least 4 light emitting parts per 1 mm width on the side of the element.
1. An LED array characterized in that the LED array is formed in a plurality of locations, and an ohmic electrode is formed on the surface of the element.