JP2000223744A - Light emitting diode array - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid short circuit between electrodes disposed with a narrow gap therebetween by forming a recess between both electrodes having one and reverse conductivity types. SOLUTION: A recess 7 is provided between a first and second electrodes 5, 4 on a light emitting part. The recess 7 is formed from the same crystal as a reverse conductivity type semiconductor layer 3 simultaneously with the time when forming the light emitting part, and covered with a protective film at its surface. The planar distance between the electrodes 5, 4 can be held long, i.e., the distance obtained owing to the recess 7 may be represented by 2×(recess 7 depth) (1-cos θ)/sin θ (=an angle (<=90 deg.) between the slope and a flat part of the recess). Thus, it is possible to form a structure not raising the drive voltage VF value with avoiding short circuit between the electrodes 5, 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 a light source for exposing a photosensitive member.

[0002]

2. Description of the Related Art FIGS. 3 and 4 show a conventional light emitting diode array. 3 and 4, reference numeral 1 denotes a substrate, 2
Is a one conductivity type semiconductor layer made of gallium arsenide, aluminum gallium arsenide, etc., 3 is a reverse conductivity type semiconductor layer, 4 is an insulating film made of a silicon nitride film or the like, and 5 is a first made of gold (Au) or gold germanium or the like. The electrode 6 is a second electrode made of gold (Au), gold germanium, or the like.

A semiconductor layer 2 of one conductivity type and a semiconductor layer 3 of opposite conductivity type are laminated on a substrate 1, and a first electrode 5 is connected to the semiconductor layer 2 of one conductivity type. This is provided by connecting a second electrode 6 to the semiconductor layer 3.

In the light emitting diode array thus configured, a semiconductor junction is formed by the semiconductor layer 2 of one conductivity type and the semiconductor layer 3 of the opposite conductivity type. For example, a current is applied from the second electrode 6 to the first electrode 5. When flowing, the minority carriers in the one-conductivity-type semiconductor layer 2 are injected into the opposite-conductivity-type semiconductor layer 3, and emit light by recombination with majority carriers in the opposite-conductivity-type semiconductor layer 3.

[0005]

However, when a light emitting diode array is constructed with the above structure, the distance between the first electrode 5 and the second electrode 6 is reduced above the light emitting portion, and short-circuiting occurs between the electrodes. And there was a reliability problem.

However, if the structure in which the one-conductivity-type semiconductor layer 2 is made long as shown in FIG. 5 in order to increase the distance between the electrodes, the size of the light-emitting diode array becomes large, resulting in high cost. In addition, there is a problem that a voltage for driving the light emitting diode array is increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the conventional device, and has solved the problem that the distance between the first electrode and the second electrode is reduced to cause a short circuit. It is intended to provide an array.

[0008]

In order to achieve the above object, in a light emitting diode array according to the first aspect, a semiconductor layer of one conductivity type and a semiconductor layer of opposite conductivity type are provided on a substrate in a stacked manner. In a light-emitting diode array provided by connecting a first electrode and a second electrode respectively to the opposite end sides of the type semiconductor layer and the opposite conductivity type semiconductor layer, the first electrode in the opposite conductivity type semiconductor layer A recess was formed between the first electrode and the second electrode.

In the above-mentioned light emitting diode array, it is preferable that the depth of the concave portion is the same as the thickness of the opposite conductivity type semiconductor layer.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a sectional view showing one embodiment of a light emitting diode array according to the present invention, and FIG. 2 is a plan view.

1 and 2, 1 is a substrate, 2 is a semiconductor layer of one conductivity type, 3 is a semiconductor layer of opposite conductivity type, 4 is an individual electrode, 5 is a common electrode, and 6 is an insulating film.

The substrate 1 is a single crystal semiconductor substrate such as silicon (Si) or gallium arsenide (GaAs) or sapphire (A).
1 ₂ O ₃ ). In the case of a single crystal semiconductor substrate, the (100) plane is set to 2 to 7 in the <011> direction.
A substrate that has been turned off is preferably used. In the case of sapphire, a C-plane substrate is preferably used.

The one conductivity type semiconductor layer 2 includes a buffer layer 2a,
It comprises an ohmic contact layer 2b and an electron injection layer 2c. The buffer layer 2a is formed to a thickness of about 2 to 4 μm, and the ohmic contact layer 2b is formed to a thickness of 0.1 to 1.0 μm.
m, and the electron injection layer 2c has a thickness of 0.2 to 0.2 m.
It is formed to a thickness of about 0.4 μm. The buffer layer 2a and the ohmic contact layer 2b are formed of gallium arsenide or the like, and the electron injection layer 2c is formed of aluminum gallium arsenide or the like. The ohmic contact layer 2b is made of one conductivity type semiconductor impurity such as silicon at 1 × 10 ¹⁶ to 10 ¹⁷ a.
tom / cm ³ , and the electron injection layer 2c contains one conductivity type semiconductor impurity such as silicon in an amount of 1 × 10 ¹⁶ to 10 ^19.
It contains about atoms / cm ³ . At this time, the Al composition of the electron injection layer 2c is formed so that x = 0.24 to 0.5. The buffer layer 2a is provided to prevent misfit dislocation due to mismatch between the lattice constant of the substrate 1 and the semiconductor layer, and does not need to contain semiconductor impurities.

The opposite conductivity type semiconductor layer 3 includes a light emitting layer 3a, a second
And a second ohmic contact layer 3c. Light emitting layer 3a and second cladding layer 3
b is formed to a thickness of about 0.2 to 0.4 μm, and the ohmic contact layer 3c is formed to a thickness of about 0.01 to 0.1 μm. The second ohmic contact layer 3c is made of gallium arsenide or the like.

The light emitting layer 3a and the second cladding layer 3b differ in the mixed crystal ratio between aluminum arsenide (AlAs) and gallium arsenide (GaAs) in consideration of the electron confinement effect and the light extraction effect. The light emitting layer 3a and the second cladding layer 3b are made of a semiconductor of opposite conductivity type such as zinc (Zn).
× 10 ¹⁶ to 10 ¹⁸ atoms / cm ³ .
The ohmic contact layer 3c contains a reverse conductivity type semiconductor impurity such as zinc at about 1 × 10 ¹⁹ to 10 ²⁰ atoms / cm ³ .

The insulating films 6a and 6b are made of silicon nitride or the like and have a thickness of about 3000 to 5000 degrees. Further, the second electrode 4 and the first electrode 5 are made of gold / chrome (Au /
AuGe / Cr) or the like, and is formed to a thickness of about 1 μm.

In the semiconductor light emitting device of the present invention, as shown in FIG. 2, the island-shaped semiconductor layers 2 and 3 composed of the one-conductivity-type semiconductor layer 2 and the opposite-conductivity-type semiconductor layer 3 are arranged on the substrate 1 in a line.
Two adjacent island-shaped semiconductor layers 2 and 3 are connected to the same individual electrode 4, and two groups such that the lower one conductivity type semiconductor layer 2 connected to the same individual electrode 4 is connected to a different first electrode 5. Are connected separately. By selecting the second electrode 4 and passing an electric current, it is used as an exposure light source for a photosensitive drum for a page printer.

In the present invention, as shown in FIG. 1, a concave portion 7 is provided between the first electrode 5 and the second electrode 4 on the light emitting section. The recess 7 is formed of the same crystal as the semiconductor layer 3 of the opposite conductivity type, and is formed simultaneously with the formation of the light emitting portion. The surface of the concave portion 7 is covered with a protective film, and the planar distance between the first electrode 5 and the second electrode 4 can be kept large according to the depth of the concave portion 7 and the shape of the concave portion 7. That is, the distance obtained by the effect of the concave portion 7 is represented by 2 × (depth of the concave portion 7) (1−cos θ) / sin θ (θ: the angle between the inclined surface of the concave portion and the flat portion (≦ 90 °)). Can be. For this reason, it is possible to realize a structure in which a short circuit between the first electrode 5 and the second electrode 4 is prevented and the VF value (drive voltage) is not increased.

Next, a method for manufacturing the above-described LED array will be described. First, a semiconductor layer 2 of one conductivity type and a semiconductor layer 3 of opposite conductivity type are sequentially laminated on a single crystal substrate 1 by MOCVD or the like.

When these semiconductor layers 2 and 3 are formed,
First, set the substrate temperature to 400 to 500 ° C. and
After forming an amorphous gallium arsenide film to a thickness of 000 °, the substrate temperature is raised to 700 to 900 ° C. to form semiconductor layers 2 and 3 having a desired thickness.

In this case, TMG ((C
H ₃ ) ₃ Ga), TEG ((C ₂ H ₅ ) ₃ Ga), arsine (AsH ₃ ), TMA ((CH ₃ ) ₃ Al), TE
A ((C ₂ H ₅ ) ₃ Al) or the like is used, and silane (SiH ₄ ), hydrogen selenide (H ₂ Se), TMZ ((CH ₃ ) ₃ Zn ) Is used, and H ₂ or the like is used as the carrier gas.

Next, the semiconductor layers 2 and 3 are patterned in an island shape so that adjacent elements are electrically separated from each other. This etching is performed by wet etching using a sulfuric acid-hydrogen peroxide-based etchant, dry etching using CCl ₂ F ₂ gas, or the like.

Next, at the same time as exposing a part of the one-conductivity-type semiconductor layer 2 on one end side, etching is performed to form the concave portion 7. The etching is performed by wet etching using a sulfuric acid-hydrogen peroxide-based etchant, dry etching using CCl ₂ F ₂ gas, or the like. When the depth of the concave portion 7 is made different from the thickness of the opposite conductive semiconductor layer 3, it may be performed separately.

Next, an insulating film made of silicon nitride is formed and patterned by plasma CVD using silane gas (SiH ₄ ) and ammonia gas (NH ₃ ).
Next, chromium and gold are formed by a vapor deposition method or a sputtering method and patterned, and further, a silane gas (SiH ₄ ) and an ammonia gas (N
This is completed by forming and patterning an insulating film made of silicon nitride using H ₃ ).

[0025]

As described above, according to the first aspect of the present invention, the recess is formed between the first electrode and the second electrode in the opposite conductivity type semiconductor layer formed on the one conductivity type semiconductor layer. Due to the formation, the distance between the first electrode and the second electrode is increased, and light emission that suppresses a short circuit between the electrodes without adding a manufacturing process step and without increasing a driving voltage. A diode array can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a light emitting diode array according to the present invention.

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

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

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

FIG. 5A shows a conventional light emitting diode array,
(B) is a diagram in which the distance between the electrodes is widened.

[Explanation of symbols]

1 ‥‥‥ substrate, 2 ‥‥‥ one conductivity type semiconductor layer, 3 ‥‥‥ reverse conductivity type semiconductor layer, 4 ‥‥‥ insulating film, 5 ‥‥‥ common electrode,
6 individual electrodes, 7 concave

Claims (2)

[Claims] 1. A semiconductor device comprising: a first conductivity type semiconductor layer and a reverse conductivity type semiconductor layer laminated on a substrate; a first electrode and a first electrode formed on opposite end portions of the one conductivity type semiconductor layer and the opposite conductivity type semiconductor layer, respectively; In a light emitting diode array provided by connecting a second electrode, a concave portion is formed between the first electrode and the second electrode in the opposite conductivity type semiconductor layer. 2. The light emitting diode according to claim 2, wherein the depth of the recess is equal to the thickness of the opposite conductivity type semiconductor layer.