JPH11112032A - Semiconductor light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor light emitting device for dissolving the decline of light emitting intensity by reducing the area of the light emitting part of a light emitting element and the decline of the light emitting intensity by covering the light emitting part of the light emitting element with an electrode. SOLUTION: In a semiconductor light emitting device for which an individual electrode 5 is connected and provided in semiconductor layers 2-4 formed on one main surface side of a semiconductor substrate 1, and a common electrode 6 is connected and provided on the other main surface side of the semiconductor substrate 1, an inclined part T inclined in the thickness direction of the semiconductor substrate 1 is provided on one main surface side of the semiconductor substrate 1, and the individual electrode 5 is connected to the semiconductor layer 4 on the inclined part T.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device, and more particularly to a semiconductor light emitting device used as an exposure light source for a photosensitive drum for a page printer.

[0002]

2. Description of the Related Art FIGS. 5 and 6 show a conventional semiconductor light emitting device.
Shown in FIG. 6 is a sectional view taken along line AA in FIG. 5 and 6, 21 is a semiconductor substrate, 22 is an island-shaped semiconductor layer, 23 is an individual electrode, and 24 is a common electrode.

The semiconductor substrate 21 is made of, for example, silicon (S
i) or a single crystal semiconductor substrate such as gallium arsenide (GaAs). The island-shaped semiconductor layer 22 is made of a compound semiconductor layer such as gallium arsenide or aluminum gallium arsenide, and includes a layer 22a containing a semiconductor impurity of one conductivity type and a layer 22b containing a semiconductor impurity of the opposite conductivity type. A semiconductor junction is formed at the interface between the layer 22a containing the semiconductor impurity of one conductivity type and the layer 22b containing the semiconductor impurity of the opposite conductivity type. This island-shaped semiconductor layer 22 is made of, for example, MOCV
A single crystal semiconductor layer made of gallium arsenide, aluminum gallium arsenide, or the like is formed by a D (metal organic chemical vapor deposition) method or an MBE (electron beam epitaxy) method, and is formed into an island shape by mesa etching or the like.

A protection film 25 made of, for example, silicon nitride (SiN _x ) is formed on the surface of the island-shaped semiconductor layer 22. The surface of the protection film 25 is made of, for example, gold (Au). Individual electrodes 23 are formed. The individual electrode 23 is connected to a semiconductor layer 22b containing a semiconductor impurity of the opposite conductivity type via a contact hole C formed in the protective film 25. This individual electrode 23
From the upper surface portion of the layer 22b containing the opposite conductivity type semiconductor impurity of the island-like semiconductor layer 22 via the wall surface portion,
The adjacent island-shaped semiconductor layers 22 are formed so as to alternately extend to the other end surface side up to near the end surface of the semiconductor substrate 21. The individual electrode 23 is connected to an external circuit at a wide portion thereof by a bonding wire or the like. A common electrode 24 is formed on almost the entire back surface of the semiconductor substrate 21.

Each light emitting diode is constituted by the island-shaped semiconductor layer 22, the individual electrode 23, and the common electrode 24. The light emitting diodes are formed on the semiconductor substrate 21 in a line. In this case, for example, the individual electrode 23 becomes the anode electrode of the light emitting diode, and the common electrode 24 becomes the cathode electrode.

In such a semiconductor light emitting device, for example, when a current flows in the forward direction from the individual electrode 23 to the common electrode 24, electrons are injected into the layer 22b containing the semiconductor impurity of the opposite conductivity type, and the one conductivity type Layer 22 containing semiconductor impurities
Holes are injected into a. Some of these minority carriers emit light by radiative recombination with majority carriers. Further, by selecting any one of the individual electrodes 23 of the light emitting elements formed in a row and causing a current to flow to emit light, the light emitting element is used, for example, as an exposure light source for a photosensitive drum for a page printer.

[0007]

In recent years, as the printing quality of a printer has been improved, the semiconductor light emitting device has been required to have higher definition. For example, as shown in FIG. in x ₁ is 10 [mu] m, a width y ₁ is required emitting element of dimensions such as 25 [mu] m.

However, when the light emitting portion of the light emitting element is reduced in area, the light emission intensity is reduced, and there has been a problem that sufficient light emission as an exposure light source for the photosensitive drum cannot be obtained.

In such a semiconductor light emitting device, the emission intensity can be improved by increasing the connection area between the individual electrode 23 and the semiconductor layer 22, but the connection area between the individual electrode 23 and the semiconductor layer 22 is increased. Then, the area of the light-emitting element is increased, and the portion that emits the strongest light is covered with the individual electrode 23. Therefore, there is a problem that the light extraction efficiency is low, and as a result, the light emission intensity is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the conventional device. The light-emitting portion of the light-emitting element is reduced in area to reduce the light-emission intensity, and the light-emitting portion of the light-emitting element is covered with an electrode. It is an object of the present invention to provide a semiconductor light emitting device in which the emission intensity is not reduced by being performed.

[0011]

According to a first aspect of the present invention, there is provided a semiconductor light emitting device, wherein an individual electrode is connected to a semiconductor layer formed on one main surface of a semiconductor substrate. In a semiconductor light emitting device provided with a common electrode connected to the other main surface of the semiconductor substrate, an inclined portion inclined in a thickness direction of the semiconductor substrate is provided on one main surface of the semiconductor substrate. Above, the individual electrodes were connected to the semiconductor layer.

In the semiconductor light emitting device according to the second aspect, a semiconductor layer of one conductivity type and a semiconductor of the opposite conductivity type are provided on one main surface side of the semiconductor substrate, and an individual electrode is connected to the semiconductor layer of the opposite conductivity type. In a semiconductor light emitting device provided by connecting a common electrode to the one conductivity type semiconductor layer, an inclined portion inclined in a thickness direction of the semiconductor substrate is provided on one main surface side of the semiconductor substrate. The individual electrode was connected to the opposite conductivity type semiconductor layer on the inclined portion, and the common electrode was connected to the one conductivity type semiconductor layer on one main surface side of the semiconductor substrate.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention according to claims 1 and 2 will be described in detail with reference to the accompanying drawings. FIG. 1 is a plan view showing an embodiment of the semiconductor light emitting device according to claim 1, and FIG. 2 is a sectional view taken along line AA in FIG. 1 and 2, 1 is a semiconductor substrate, 2 is a buffer layer, 3 is a semiconductor layer of one conductivity type, 4 is a semiconductor layer of opposite conductivity type, 5 is an individual electrode, 6 is a common electrode, and 7 is a protective film. Each semiconductor layer is composed of the buffer layer 2, the one conductivity type semiconductor layer 3, and the opposite conductivity type semiconductor layer 4.

The semiconductor substrate 1 is made of, for example, silicon (Si).
And a single crystal semiconductor substrate of gallium arsenide (GaAs) or the like.
It contains about 0 ¹⁶ to 10 ¹⁸ atoms · cm ^-3 . This semiconductor substrate 1 has a thickness of, for example, about 300 to 400 μm. On one main surface side of the semiconductor substrate 1, an inclined portion T inclined in the thickness direction of the semiconductor substrate 1 is provided. The inclined portion T is formed, for example, by covering a part of the semiconductor substrate 1 with a photomask and removing the other part by etching. This etching may be either wet etching or dry etching. When an individual electrode 5 described later is provided on one side of the substrate 1, the inclined portion T may be formed only on one side of the semiconductor substrate 1. The inclined portion T is formed, for example, to have a thickness h ₁ of about 3.5 μm and a width w ₁ of about 5 μm.

On the semiconductor substrate 1, a buffer layer 2,
One conductivity type semiconductor layer 3 and reverse conductivity type semiconductor layer 4 are formed by sequentially laminating.

The buffer layer 2 is provided to reduce misfit dislocations due to a difference in lattice constant between the semiconductor substrate 1 and the one conductivity type semiconductor layer 3, and has a thickness of 1 to 4 μm.
m of gallium arsenide or the like. This buffer layer 2
Has a conductivity type semiconductor impurity of 1 × 10 ¹⁶ to 10 ¹⁸ at
oms · cm ^-3 . A plurality of buffer layers 2 may be provided in order to more effectively reduce misfit dislocations.

On the buffer layer 2, a one conductivity type semiconductor layer 3 is provided. The one conductivity type semiconductor layer 3 is made of gallium arsenide or aluminum gallium arsenide (Al _x Ga _{1 -x} A
s) or the like, and one conductivity type semiconductor impurity such as silicon (Si) or selenium (Se) is 1 × 10 ¹⁶ to 1
It contains about 0 ¹⁹ atoms · cm ^-3 . This one conductivity type semiconductor layer 3 is formed to a thickness of about 0.3 to 3 μm.

On the one conductivity type semiconductor layer 3, an opposite conductivity type semiconductor layer 4 is formed. The opposite conductivity type semiconductor layer 4 is also made of a compound semiconductor layer such as aluminum gallium arsenide (Al _y Ga _{1 -y} As), and contains a reverse conductivity type semiconductor impurity such as zinc (Zn) at 1 × 10 ¹⁶ to 10 ¹⁹ atoms · cm. ^-3
Content. The opposite conductivity type semiconductor layer 4 has a thickness of 0.1 to 3
It is formed to a thickness of about μm. The one conductivity type semiconductor layer 3
And the opposite conductivity type semiconductor layer 4 has a mixed crystal ratio, for example, in order to more effectively perform the effect of confining carriers and the effect of extracting light.
Alternatively, each layer may be formed of a plurality of layers having different optical energy band gaps.

When the buffer layer 2, the one conductivity type semiconductor layer 3, and the opposite conductivity type semiconductor layer 4 are sequentially laminated on the semiconductor substrate 1, the inclined portion T of the semiconductor substrate 1 is directly connected to the semiconductor layers 2 to 4. Then, the inclined portion is formed also on the surface portion of the opposite conductivity type semiconductor layer 3. The buffer layer 2, the one conductivity type semiconductor layer 3, and the opposite conductivity type semiconductor layer 4 are formed in an island shape for each light emitting element.

The semiconductor layers 2 to 4 are covered with a protective film 7 made of, for example, a silicon nitride (SiN _x ) film.

Gold and chromium (Au / Au) are applied to the opposite conductivity type semiconductor layer 4 through the contact holes formed in the protective film 7.
An individual electrode 5 made of Cr or the like is connected. The individual electrodes 5 are connected on the inclined portion T of the semiconductor substrate 1. On the other main surface side of the semiconductor substrate 1, gold and chromium (Au)
A semiconductor impurity is added at a high concentration to a connection portion between the common electrode 6 made of / Cr) or the like and the semiconductor substrate 1 in order to obtain an ohmic contact.

As described above, when the individual electrode 5 is connected to the opposite conductivity type semiconductor layer 4 on the inclined portion T of the semiconductor substrate 1, of the interface between the one conductivity type semiconductor layer 3 and the opposite conductivity type semiconductor layer 4,
Although light is emitted at three places: a high place area A, an inclined area B, and a low place area C, since the semiconductor layers 2 to 4 are formed to be inclined in the inclined area B, light emission in the inclined area B is also external. Can be effectively taken out. That is, in the conventional device, only the light emission in the high place area A can be extracted, but in the product of the present invention, the light emission in the inclined area B can also be extracted, and the emission intensity can be improved by about 20% as compared with the conventional structure. Do you get it.

Next, an example of a method for manufacturing a semiconductor light emitting device according to claim 1 will be described. First, an inclined portion T is formed on one main surface side of the semiconductor substrate 1. This inclined portion T covers a predetermined region on one main surface side of the semiconductor substrate 1 with a photomask, and is etched with a hydrofluoric-nitric acid or sulfuric acid-based hydrogen peroxide-based etchant. In this case, if the plane orientation of the semiconductor substrate 1 is determined so that the light emitting elements are arranged in the <001> direction of the semiconductor substrate 1, the extraction direction of the individual electrode 4 is inevitably mesa-etched, and the inclined portion T is formed. Will be formed.

Next, the buffer layer 2, the one conductivity type semiconductor layer 3, and the opposite conductivity type semiconductor layer 4 are sequentially laminated by MOCVD or the like. When a silicon substrate is used as the semiconductor substrate 1, for example, a natural oxide film on
Removed at a high temperature of 00 ° C., and then grown an amorphous gallium arsenide film serving as a nucleus at a low temperature of 450 ° C. or less to a thickness of 100 to 500 ° C., and then heated to 500 to 700 ° C.
A gallium arsenide single crystal film is formed (two-step growth method). The growth is interrupted in this gallium arsenide film,
Crystal defects such as dislocations are reduced by repeating high-temperature annealing at ℃ and rapid cooling to 600 ° C. or lower (thermal cycle method). Next, the remaining buffer layers 2 are continuously formed until a predetermined thickness is obtained, and the one conductivity type semiconductor layer 3 and the opposite conductivity type semiconductor layer 4 are sequentially formed.

In the case of forming by MOCVD, gallium (Ga) source gas is trimethylgallium ((C
H ₃ ) ₃ Ga) and the like, arsine (AsH ₃ ) and the like as arsenic (As) source gas, and trimethylaluminum ((CH ₃ ) ₃ Al) as aluminum (Al) source gas Is used. Silane (Si) is used as the n-type semiconductor impurity for controlling the conductivity type.
H ₄ ), and p-type semiconductor impurities include dimethyl zinc ((CH ₃ ) ₂ Zn).

As described above, the buffer layer 2, the one conductivity type semiconductor layer 3, and the opposite conductivity type semiconductor layer 4 are sequentially formed on the entire surface or a part of the semiconductor substrate 1, and then formed into an island shape by etching or the like. Then, after forming a protective film 6 made of a silicon nitride film or the like by MOCVD or the like, a contact hole portion is formed, and the individual electrode 4 and the common electrode 5 are formed.

FIGS. 3 and 4 are views showing one embodiment of the semiconductor light emitting device according to claim 2, FIG. 3 is a plan view, and FIG. 4 is a sectional view taken along line AA in FIG. 3 and 4, 1 is a semiconductor substrate, 2 is a buffer layer, 3 is a semiconductor layer of one conductivity type, 4 is a semiconductor layer of the opposite conductivity type, 5 is an individual electrode, 6
Is a common electrode, 7 is a protective film, and T is an inclined portion.

In the semiconductor light emitting device according to the second aspect, the inclined portion T is formed on one main surface side of the semiconductor substrate 1 so that the buffer layer 2, the one conductivity type semiconductor layer 3, and the opposite conductivity type semiconductor layer 4 are formed.
Is formed, and the individual electrode 5 is connected to the opposite-conductivity-type semiconductor layer 4 on the inclined portion T. This is almost the same as the semiconductor light emitting device according to claim 1, but the semiconductor according to claim 2 In the light emitting device, the common electrode 6 is formed on one main surface side of the semiconductor substrate 1 on which the semiconductor layers 2 to 4 are formed.

Even with such a configuration, the light emitted from the light emitting region B is extracted to the front surface side of the semiconductor substrate 1 and the light emission intensity is improved. Further, the common electrode 6 is connected to the individual electrode 5 of the semiconductor substrate 1.
The common electrode 6 and the individual electrode 5 can be formed in a single process by forming them on one main surface side on which is formed, thereby simplifying the manufacturing process.

[0030]

As described above, according to the semiconductor light emitting device of the first aspect, the inclined portion inclined in the thickness direction of the semiconductor substrate is provided on one main surface side of the semiconductor substrate. Since the individual electrode is connected to the semiconductor, light emitted immediately below the connection between the electrode and the semiconductor layer can also be extracted,
As a result, the emission intensity of the entire light emitting element is improved. Further, since the connection portion between the electrode and the semiconductor layer is inclined, the connection area between the electrode and the semiconductor layer can be increased without increasing the area of the light emitting element when viewed in plan.

Further, according to the semiconductor light emitting device of the present invention, an inclined portion inclined in the thickness direction of the semiconductor substrate is provided on one principal surface side of the semiconductor substrate, and the individual electrode is reversely conductive on the inclined portion. Connection between the electrode and the semiconductor layer without increasing the area of the light emitting element in plan view because the common electrode is connected to the one-conductivity type semiconductor layer on one main surface side of the semiconductor substrate while being connected to the semiconductor layer. The area can be increased, and the common electrode and the individual electrode can be formed in one process, which simplifies the manufacturing process.

[Brief description of the drawings]

FIG. 1 is a plan view showing one embodiment of a semiconductor light emitting device according to claim 1;

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

FIG. 3 is a view showing one embodiment of a semiconductor light emitting device according to claim 2;

FIG. 4 is a sectional view taken along line AA in FIG.

FIG. 5 is a plan view showing a conventional semiconductor light emitting device.

FIG. 6 is a sectional view taken along line AA in FIG.

FIG. 7 is an enlarged view showing a light emitting element portion in a conventional semiconductor light emitting device.

[Explanation of symbols]

1 semiconductor substrate, 2 buffer layer, 3 one conductivity type semiconductor layer, 4 reverse conductivity type semiconductor layer, 5 layer
Individual electrode, 6 mm common electrode, 7 mm protective film

Claims (2)

[Claims] In a semiconductor light emitting device, an individual electrode is connected to a semiconductor layer formed on one main surface of a semiconductor substrate and a common electrode is connected to another main surface of the semiconductor substrate. A semiconductor light emitting device, wherein an inclined portion inclined in a thickness direction of the semiconductor substrate is provided on one principal surface side of the semiconductor substrate, and the individual electrode is connected to the semiconductor layer on the inclined portion. 2. The semiconductor device according to claim 1, further comprising: a first conductive type semiconductor layer and a reverse conductive type semiconductor laminated on one main surface side of the semiconductor substrate; and an individual electrode connected to the reverse conductive type semiconductor layer. In a semiconductor light emitting device provided with a common electrode connected to a layer, an inclined portion inclined in a thickness direction of the semiconductor substrate is provided on one principal surface side of the semiconductor substrate, and the individual electrode is inverted on the inclined portion. Connect to the conductive semiconductor layer,
A semiconductor light emitting device, wherein the common electrode is connected to the one conductivity type semiconductor layer on one main surface side of the semiconductor substrate.