JPH05243609A - Semiconductor light emitting device - Google Patents

Abstract

PURPOSE:To have a large area of a semiconductor junction part while having a highly minute light emitting device by forming a V-shaped groove on an insular part provided on a semiconductor substrate and covering an insular part excepting this V-shaped groove with an electrode. CONSTITUTION:An insular part I consisting of at least two layers 3, 4 of different conduction types is provided on a semiconductor substrate 1, and a V-shaped groove G is formed on this insular part I while covering an insular part excepting the V-shaped groove G with an electrode so that this V-shaped groove G may become a light take-out part. Thereby, light radiated near a semiconductor junction part is taken out from a V-shaped groove G part. In this case, since the insular part I is covered with an electrode excepting one side or an opposing side, a current flows ranging over the whole of the semiconductor junction part of the insular part I so as to have the strong luminous intensity. Further, an area of the semiconductor junction part can be made of a large area by shortening the length of the V-shaped groove G while making the insular parts I on both sides of the V-shaped groove G and making a light emitting device highly minute by intensifying luminous strength.

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,
For example, the present invention relates to a semiconductor light emitting element used as a light source for a photosensitive drum of a page printer.

[0002]

2. Description of the Related Art In recent years, semiconductor light emitting devices have been manufactured by MOCVD.
With the progress of compound semiconductor crystal growth techniques such as the (metalorganic chemical vapor deposition) method and the MBE (molecular beam epitaxy) method, active research has been conducted.

A conventional semiconductor light emitting device will be described with reference to FIG. FIG. 4 is a cross-sectional view of a conventional semiconductor light emitting device, where 21 is a single crystal semiconductor substrate made of, for example, silicon (Si) containing one conductivity type impurity, and 22 is a buffer layer made of gallium arsenide film (GaAs) or the like. , 23 is a first semiconductor layer made of an aluminum gallium arsenide film (Al _x Ga _{1 -x} As) having the same conductivity type as the semiconductor substrate 21, and 24 is an aluminum gallium arsenide film (Aly _y containing an impurity of opposite conductivity type). Ga _1-y As) or the like, 25 is a second semiconductor layer, 25 is an ohmic contact layer made of a gallium arsenide film containing a large amount of impurities of opposite conductivity type, 2
Reference numeral 6 is a protective layer made of, for example, a silicon nitride film (SiN _x ). An upper electrode 27 is formed on the protective layer 26, and the ohmic contact layer 25 and the upper electrode 27 are connected via the contact hole 26a of the protective layer 26. A lower electrode 28 for making ohmic contact with the semiconductor substrate 21 is provided on the back surface side of the semiconductor substrate 21. In addition, the buffer layer 2
2, the first semiconductor layer 23, the second semiconductor layer 24, and the ohmic contact layer 25 are formed in an island shape,
One light emitting element is composed of this one island-shaped portion.

The operation of the semiconductor light emitting device having the above structure will be described. The first semiconductor layer 23 is made N-type, the second semiconductor layer 24 is made P-type, the upper electrode 27 is made positive, and the lower part is made lower. When a voltage is applied in the forward bias direction with the electrode 28 being negative, minority carriers are injected from the N-type first semiconductor layer 23 to the P-type second semiconductor layer 24, and the second semiconductor layer 24 and the second semiconductor layer 24 Carriers are recombined at the interface of the semiconductor junction, which is the interface of the one semiconductor layer 23, on the side of the second semiconductor layer 24 to emit light. The emitted light is extracted to the outside through the second semiconductor layer 24 and the protective layer 26.

[0005]

However, in this conventional semiconductor light emitting device, the light emitted in the vicinity of the semiconductor junction is taken out from the upper part of the island-shaped portion, so that the upper electrode 27 should not interfere with the extraction of light. It has to be formed in a small area, and as a result, there is a problem in that the current flow locally at the semiconductor junction and the emission intensity is weakened.

Further, in this conventional semiconductor light emitting device, in order to increase the light emission intensity, it is sufficient to make the island-shaped portion large so that the semiconductor junction has a large area. There is a problem that it hinders the high definition.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and is characterized in that at least two layers having different conductivity types are formed on a semiconductor substrate. An island-shaped portion made of a semiconductor layer is provided, a V-shaped groove is formed in the island-shaped portion, and the island-shaped portion other than the V-shaped groove is covered with an electrode so that the V-shaped groove serves as a light extraction portion. There is a point.

[0008]

With the above structure, the light emitted near the semiconductor junction is extracted from the V-shaped groove.
In this case, since the island-shaped portion is covered with the electrodes except for one side surface or the opposite side surface, a current flows through the entire semiconductor junction portion of the island-shaped portion, and the emission intensity becomes extremely strong. Further, by shortening the length of the V-shaped groove and increasing the area of the island-shaped portions on both sides of the V-shaped groove, it is possible to increase the area of the semiconductor junction without increasing the size of the light emitting dot. Higher definition can be achieved while increasing strength.

[0009]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1A is a perspective view showing an embodiment of a semiconductor light emitting device according to the present invention, and FIG. 1B is a sectional view showing one light emitting device portion. Buffer layer, 3 is a first semiconductor layer, 4 is a second semiconductor layer, 5 is an ohmic contact layer, 6 is a protective layer, 7 is an upper electrode,
Reference numeral 8 is a lower electrode.

The semiconductor substrate 1 is composed of, for example, a single crystal semiconductor substrate made of a III-V group compound semiconductor such as gallium arsenide (GaAs) or a single crystal silicon substrate. A III-V group compound semiconductor substrate such as gallium arsenide is advantageous in manufacturing a semiconductor light emitting device, but a single crystal silicon substrate is advantageous in terms of cost, mechanical strength, and increase in area. The semiconductor substrate 1, one conductivity type impurity, in the case of the example, N-type, antimony (Sb), arsenic (As), phosphorus (P) impurities such as 10 ¹⁶ to 10 ¹⁸
Pieces / cm ³ order is contained, for example, when the P-type, boron (B) to impurities contained approximately 10 ¹⁶ to 10 ¹⁸ / cm ^3, such as.

The buffer layer 2 is made of gallium arsenide or the like.
Comprised of III-V group compound semiconductor layers, TMGa gas, As
MO using H ₃ gas and impurity element source gas
It is formed by the CVD method or the like. This buffer layer 2 is
When single crystal silicon is used as the semiconductor substrate 1, it is formed to prevent misfit transition due to mismatch of lattice constants between the semiconductor substrate 1 and the first semiconductor layer 3. Such as gallium arsenide
It is not necessary when using a III-V compound semiconductor substrate.

A first semiconductor layer 3 containing an impurity of one conductivity type is formed on the buffer layer 2. The first semiconductor layer 3 is made of, for example, aluminum gallium arsenide (Al _x Ga _{1 -x} As), and is made of silicon (S
i), a donor made of germanium (Ge), tin (Sn) or the like or an acceptor made of zinc (Zn), cadmium (Cd) or the like is contained at about 10 ¹⁶ to 10 ¹⁸ pieces / cm ³ . This first semiconductor layer 3 is also made of TMGa gas, As.
MO using H ₃ gas and impurity element source gas
It is formed by the CVD method or the like.

A second semiconductor layer 4 is formed on the first semiconductor layer 3. The second semiconductor layer 4 may, for example, aluminum gallium arsenide (Al _y Ga _1-y A
s) and the like, and contains donors of silicon (Si), germanium (Ge), tin (Sn), etc., or acceptors of zinc (Zn), cadmium (Cd), etc. of about 10 ¹⁶ to 10 ¹⁸ / cm ^3. Let The second semiconductor layer 4 contains a semiconductor impurity so as to have a conductivity type opposite to that of the first semiconductor layer 3, and the first semiconductor layer 3 and the second semiconductor layer 4 form a semiconductor junction. .. The first semiconductor layer 3 is also formed by the MOCVD method using TMGa gas, AsH ₃ gas, impurity element source gas, and the like.

An ohmic contact layer 5 is formed on the second semiconductor layer 4. The ohmic contact layer 5 is formed of a gallium arsenide film (GaAs) containing a high concentration of semiconductor impurities.

The buffer layer 2, the first semiconductor layer 3, the second semiconductor layer 4, and the ohmic contact layer 5 are
The island-shaped portion I is formed into a plurality of islands, and a V-shaped groove G is formed substantially at the center of the island-shaped portion I. Islands I and V
The groove G has sulfuric acid (H ₂ SO ₄ ), hydrogen peroxide (H
₂ O ₂ ), a mixed solution of water (H ₂ O) or the like is used to select the plane orientations of the semiconductor layers 2 to 5 and perform mesa etching.

A transparent protective layer 6 is formed on the side surface of the island portion I, the V-shaped groove portion G, and the semiconductor substrate 1. The protective layer 6 is, for example, a silicon nitride film (Si
N _x ) or a silicon oxide film (SiO ₂ ). The protective layer 6 is formed by, for example, a plasma CVD method using silane gas (SiH ₄ ) and ammonia gas (NH ₃ ) or laughing gas (N ₂ O).

An electrode 7 is formed from the upper portion of the island portion I to the side surface portion except for the V-shaped groove G portion. This electrode 7
Is formed of a two-layer structure of chromium (Cr) and gold (Au), silver (Ag), an alloy of silver and zinc (Zn), or the like, and is formed by a vacuum deposition method, a sputtering method, or the like.

A lower electrode 8 is formed on the back surface side of the semiconductor substrate 1. This lower electrode 8 is also made of chromium (C
It is formed of a two-layer structure of r) and gold (Au), silver (Ag), an alloy of silver and zinc (Zn), or the like, and is formed by a vacuum deposition method, a sputtering method, or the like.

In this way, from the upper part of the island portion I to the side surface part,
When the electrode 7 is formed excluding the V-shaped groove G portion, the light emitted from the semiconductor junction portion in the island-shaped portion I is reflected on the back surface of the electrode 7 in the island-shaped portion I, and only the V-shaped groove G portion is formed. Taken from.
The light extracted from the V-shaped groove G portion is reflected by the facing surface of the V-shaped groove G and is extracted above the island-shaped portion I. In this case, since the electrode 7 is formed on almost the entire surface of the island-shaped portion I, the current flows evenly over a wide region of the semiconductor junction, the emission intensity is increased, and the V-shaped groove G is formed on both sides. By increasing the area of the island-shaped portion I, the area of the semiconductor junction can be further increased, and a highly precise light emitting device with strong emission intensity can be obtained.

FIG. 2 is a diagram for explaining a second embodiment of the semiconductor light emitting device according to the present invention. In this embodiment, the island-shaped portion I is formed in a strip shape, a plurality of V-shaped grooves G _{1 to} G ₄ are formed in the island-shaped portion I, and electrodes adjacent to each other in the lateral direction are commonly used. 7a to 7c are formed, and the electrodes 7d to 7f are combed so that the electrodes adjacent to each other in the lateral direction are commonly used in a portion facing the electrodes 7a to 7c, and the electrodes 7a to 7c are offset by one. It is formed in a tooth shape. Thus formed and, when a current flows by selecting electrodes 7b, V-shaped groove G _2, G _3, G ₄ moieties are luminescent constitutes one dot, when electric current by selecting the electrode 7e , V-shaped groove G
_{The 1} , G ₂ , and G ₃ portions form one dot and emit light. In this case, since the V-shaped grooves G ₂ and G ₃ emit light in common, there is no gap between the emission dots in the scanning direction, and the emission dots can be made finer.

FIG. 3A is a view for explaining a third embodiment of the semiconductor light emitting device according to the present invention, and FIG. 3B is a sectional view. In this embodiment, the island-shaped portion I is formed in a strip shape, and a plurality of V-shaped grooves G ₁ to G ₁ to are formed in the island-shaped portion I.
G ₃ and V-shaped grooves G _{4 to} G ₆ are formed separately, and the electrode 7 a is formed so that the V-shaped grooves G ₁ , G ₂ , and G ₃ emit light as one dot, and the V-shaped groove G ₄ is formed. , G ₅ and G ₆ are 1
The electrode 7b is formed so as to emit light as dots. Also, the opposite one side of the V-shaped grooves G ₁ and G _{3 and} the opposite one side of the V-shaped grooves G ₄ and G ₆ are covered with an electrode material, and the V-shaped grooves G ₁ , G ₃ and V-shaped groove G are covered. ₄ , light emitted from one side of G ₆ is reflected and directed toward the upper part of the island portion I. By configuring in this way,
The light emitted from one side of the V-shaped grooves G ₁ and G ₃ and the V-shaped grooves G ₄ and G ₆ can also be efficiently directed to above the island-shaped portion I.

[0023]

As described above, according to the semiconductor light emitting device of the present invention, the island-shaped portion formed of at least two semiconductor layers having different conductivity types is provided on the semiconductor substrate, and the island-shaped portion is provided with V. Since the V-shaped groove is formed and the portions other than the V-shaped groove are covered with the electrodes so that the V-shaped groove serves as a light extraction portion, a current flows through the entire semiconductor junction portion of the island-shaped portion. ,
The emission intensity is extremely strong. In addition, by shortening the length of the V-shaped groove and increasing the area of the island-shaped portions on both sides of the V-shaped groove, it is possible to increase the area of the semiconductor junction, thereby increasing the emission intensity and achieving high definition. You can also

[Brief description of drawings]

1A is a perspective view showing an embodiment of a semiconductor light emitting device according to the present invention, and FIG. 1B is a sectional view of the same.

FIG. 2 is a perspective view showing another embodiment of the semiconductor light emitting device according to the present invention.

3A is a perspective view showing another embodiment of the semiconductor light emitting device according to the present invention, and FIG. 3B is a sectional view of the same.

FIG. 4 is a cross-sectional view showing a conventional semiconductor light emitting device.

[Explanation of symbols]

1 ... Semiconductor substrate, 3 ... First semiconductor layer, 4 ...
-Second semiconductor layer, 7 ... Electrode, I ... Island portion, G
... V-shaped groove.

Claims (1)

[Claims] 1. An island-shaped portion composed of at least two semiconductor layers having different conductivity types is provided on a semiconductor substrate, and a V-shaped groove is formed in the island-shaped portion, and the V-shaped groove serves as a light extraction portion. A semiconductor light emitting device in which the island-shaped portion other than the V-shaped groove is covered with an electrode.