JP3450992B2 - Semiconductor light emitting device - Google Patents

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 a light source for discharging a photosensitive drum of a page printer, a light source for reading an original of a facsimile, and the like.

[0002]

2. Description of the Related Art A conventional semiconductor light emitting device is shown in FIGS.
Shown in. 3 and 4, 11 is a single crystal substrate,
Reference numeral 12 is a semiconductor layer of one conductivity type, 13 is a semiconductor layer of an opposite conductivity type, 1
Reference numeral 4 is an individual electrode, and 15 is a common electrode. Single crystal substrate 11
Is made of silicon or gallium arsenide, and the one-conductivity-type semiconductor layer 12 is made of gallium arsenide or aluminum gallium arsenide containing silicon (Si), tellurium (Te), selenium (Se), or the like. Is made of gallium arsenide or aluminum gallium arsenide containing zinc (Zn) or cadmium (Cd). The opposite conductivity type semiconductor layer 13 is formed in a smaller area than the one conductivity type semiconductor layer 12 so that one end side of the one conductivity type semiconductor layer 12 is alternately exposed for each adjacent one conductivity type semiconductor layer 12. The one conductivity type semiconductor layers 12 exposed on the same side are connected to the same common electrode 15. In addition, different common electrodes 15
The opposite conductivity type semiconductor layer 13 on the adjacent one conductivity type semiconductor layer 12 connected to is connected to the same individual electrode 14.

A semiconductor junction is formed at the interface between the one conductivity type semiconductor layer 12 and the opposite conductivity type semiconductor layer 13, and the individual electrode 1
A large number of light emitting elements 16 are selected to emit light by selecting a combination of 4 and the common electrode 15 and passing an electric current.

[0004]

However, in this conventional semiconductor light emitting device, although a large number of light emitting elements 16 are formed in a row on the single crystal substrate 11, each light emitting element 16 is formed.
Are formed such that the side wall portions thereof are parallel to the end faces of the single crystal substrate 11 in the longitudinal direction and the lateral direction, and therefore the interval between the light emitting elements 16 is increased, and one light emitting element 16 is formed.
Had to be formed small, and there was a problem that it was difficult to achieve high definition. That is, the light emitting element 1 at 600 dpi
6 is formed, the pitch of the light emitting elements 16 is p = 42.
Although the width of the light emitting element 16 must be 3 μm, the mesa portion of the side wall of the light emitting element 16 must be formed with a width of about 5 μm, and the element width of the light emitting element 16 is at most 32.3 μm.
There is a problem that only m can do it.

Further, in the conventional semiconductor light emitting device, the light emitting element 16 is formed in a rectangular shape, and a current flows from above the light emitting element 16 toward the opposite side, but the side wall of the light emitting element 16 is shared by the individual electrode 14 and the common side. Since it is positioned in parallel or perpendicular to the electrode 15, the emitted light is transmitted through the side wall of the light emitting element 16, and there is a problem that the light extraction efficiency onto the light emitting element 16 is poor.

The present invention has been invented in view of such problems, and it is difficult to achieve high definition of the light emitting device,
It is an object of the present invention to provide a semiconductor light emitting device that solves the problem of the conventional device that the light extraction efficiency is poor.

[0007]

To achieve the above object, in a semiconductor light emitting device according to the present invention, an island-shaped semiconductor layer composed of a semiconductor layer of one conductivity type and a semiconductor layer of opposite conductivity type is formed on a single crystal substrate. A plurality of columns are formed in the <001> direction on the single crystal substrate, and the side wall portions of the island-shaped semiconductor layer are formed so as to face the <011> direction and the <0-11> direction of the single crystal substrate. A semiconductor light-emitting device in which a common electrode is connected to one end side of one conductivity type semiconductor layer and an individual electrode is connected to the other end side of an opposite conductivity type semiconductor layer, wherein the one conductivity type semiconductor layer is provided. The opposite conductivity type semiconductor layer is formed on the one conductivity type semiconductor layer such that the end part on the <010> direction side in is exposed alternately for each adjacent one conductivity type semiconductor layer, and the same end side is formed. Each exposed one conductivity type semiconductor layer is connected to the same common electrode. And it was connected to the same individual electrodes each opposite conductivity type semiconductor layer adjacent on different common one conductivity type connected to the electrode semiconductor layer.

In the semiconductor light emitting device according to the present invention,
It is desirable to continuously form one conductive type semiconductor layer below the opposite conductive type semiconductor layer connected to the same individual electrode.

Further, in the semiconductor light emitting device according to the present invention, it is desirable that adjacent ends of the island-shaped semiconductor layers partially overlap each other in the arrangement direction of the island-shaped semiconductor layers.

[0010]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below in detail with reference to the accompanying drawings. In the present specification, the crystal orientation <-1> means bar 1. 1 is a plan view showing an embodiment of a semiconductor light emitting device according to the present invention.
(A) is an enlarged plan view showing one light emitting element,
FIG. 2B is a sectional view. 1 and 2,
Reference numeral 1 is a single crystal substrate, 2 is a one conductivity type semiconductor layer, 3 is a reverse conductivity type semiconductor layer, 4 is an individual electrode, and 5 is a common electrode. The single crystal substrate 1 is a semiconductor substrate such as silicon or gallium arsenide,
Alternatively, it is made of an insulating substrate such as sapphire. This single crystal substrate 1 has a (100) plane substrate or (10) plane.
0) surface is 2 to <001> direction or <011> direction
A substrate that is turned off by 8 ° is used.

The one conductivity type semiconductor layer 2 is made of gallium arsenide, aluminum gallium arsenide, or the like, and is made of silicon (S
i) or one conductivity type semiconductor impurity such as tellurium (Te) or selenium (Se) is added at 1 × 10 ¹⁶ to 10 ¹⁸ atoms · cm ^−3.
Contain to some extent. A thickness of about 2 μm is provided between the single crystal substrate 1 and the one-conductivity type semiconductor layer 2 in order to discontinue misfit dislocations due to a difference in lattice constant between the single-crystal substrate 1 and the one-conductivity type semiconductor layer 2. It is desirable to provide the above buffer layer. Although not shown, it is desirable to provide an ohmic contact layer containing a high concentration of one conductivity type semiconductor impurity at a contact portion with a common electrode 5 described later.

The reverse conductivity type semiconductor layer 3 is made of gallium arsenide, aluminum gallium arsenide, or the like, and contains a reverse conductivity type semiconductor impurity such as zinc (Zn) or cadmium (Cd).
× 10 ¹⁶ to 10 ²⁰ atoms · cm ^{−3 is} contained. The lower layer portion of the reverse conductivity type semiconductor layer 3 has an energy band gap higher than that of the upper layer portion of the reverse conductivity type semiconductor layer 3 or the upper layer portion of the one conductivity type semiconductor layer 2 in order to confine carriers and obtain high-luminance light emission. It is desirable to form a so-called double hetero structure by using a narrow material. Reverse conductivity type semiconductor layer 3
When the lower layer portion is formed of, for example, gallium arsenide, the upper and lower layers thereof may be formed of, for example, aluminum gallium arsenide, and when the lower layer portion of the reverse conductivity type semiconductor layer 3 is formed of, for example, aluminum gallium arsenide, the upper and lower layers thereof may be formed. Aluminum gallium arsenide, which has a higher mixed crystal ratio of aluminum arsenide, may be used. Further, this reverse conductivity type semiconductor layer 3
Among them, it is desirable that the contact portion with the individual electrode 4 to be described later contains a high concentration of a reverse conductivity type semiconductor impurity in order to make an ohmic contact. The light emitting layer formed in the opposite conductivity type semiconductor layer 3 and the cladding layers formed above and below the light emitting layer are formed to have a thickness of about 0.1 to 2 μm. Further, the ohmic contact layer may have a thickness of several hundred to several thousand Å.

The one-conductivity-type semiconductor layer 2 and the opposite-conductivity-type semiconductor layer 3 are laminated to form a large number of islands. Island part 6
Are formed in an array along the <001> direction on the (100) plane of the single crystal substrate 1, but the sidewall portions of the island-shaped portions 6 are <011.
It is formed so as to face the> direction and the <0-11> direction. In this way, the island-shaped portions 6 are formed on the (100) plane of the single crystal substrate 1 with <0.
When the side wall portions of the island-shaped portion 6 are formed so as to be oriented along the <011> direction and the <0-11> direction while being arrayed along the 01> direction, all the side wall portions of the island-shaped portion 6 are formed of the single crystal substrate 1. The mesa structure has a cutting angle of 50 to 70 °,
In addition to facilitating the formation of the protective film 7 and the electrodes 4 and 5, the adjacent end portions of the plurality of island-shaped portions 6 can be arranged in an overlapping manner in the arrangement direction of the island-shaped portions 6 to form a light emitting element at 600 dpi. Even if it does, the apparent width of the light emitting element is 42.3μ.
m, and high definition is possible.

The opposite-conductivity-type semiconductor layer 3 is deeper than the one-conductivity-type semiconductor layer 2 so that the end of the one-conductivity-type semiconductor layer 2 on the <010> direction side is alternately exposed for each adjacent one-conductivity-type semiconductor layer 2. It is formed in a small area. The common electrode 5 is connected to the exposed portion of the one-conductivity-type semiconductor layer 2. In this case, the one conductivity type semiconductor layers 2 exposed on the same side are connected to the same common electrode 5, and are distributed to both sides in the longitudinal direction of the single crystal substrate 1 and connected to the two common electrodes 5. Further, one individual electrode 4 is provided on the other end side of the two opposite conductivity type semiconductor layers 3 on the adjacent one conductivity type semiconductor layers 2 connected to different common electrodes 5.
Are connected. The electrodes 4, 5 of the island-shaped semiconductor layer 6
The part not covered with is the light extraction surface.

In this case, by selecting a combination of the individual electrode 4 and the common electrode 5 and applying a current to the semiconductor junction, each light emitting element selectively emits light. That is, when a current is passed through the semiconductor junction in the forward direction, the potential barrier is lowered, and electrons in the n-side conduction band are injected as minority carriers into the p-side conduction band as minority carriers, where holes of majority carriers are generated. Recombines and emits light. In this case, the current I flows from one corner of the island-shaped semiconductor layer 6 to the opposite corner (electrons are in the opposite direction), and the emitted light H _V is reflected by the wall surface W of the island-shaped semiconductor layer 6 and is island-shaped. Since it is guided to the central portion of the semiconductor layer 6,
Light extraction efficiency is improved and light is emitted with high brightness as compared with a conventional light emitting element in which a current is passed from one side to the opposite side.

In the adjacent island-shaped semiconductor layers 6, the opposite conductivity type semiconductor layers 3 may be completely separated, and the adjacent one conductivity type semiconductor layers 2 connected to different common electrodes 5 are continuous. May be.

In the semiconductor light emitting device as described above, the one conductivity type semiconductor layer 2 is formed on the single crystal substrate 1 by the MOCVD method or the MBE method.
And a semiconductor layer 3 of the opposite conductivity type is formed, and the side wall of the semiconductor layer 3 has a thickness of <01.
1> direction and <0-11> direction are mesa-etched with an acid-based etchant, and then opposite conductivity type semiconductors are formed so that end portions of the one conductivity type semiconductor layer 2 on the <010> direction are alternately exposed. Etching part of layer 3 and then plasma CVD
After forming a protective film 7 by a method such as a method to form a through hole in a predetermined portion, an individual electrode 4 and a common electrode 5 made of gold germanium, gold chrome, etc. are formed by a vacuum deposition method or the like and patterned. It In the case of forming by the MOCVD method, the raw material of gallium is ((CH ₃ ) ₃ G
a) or ((C ₂ H ₅ ) ₃ Ga) or the like is used, AsH ₃ or the like is used as a raw material of arsenic, and ((CH ₃ ) ₃ Al) or ((C ₂ H ₅ ) ₃
Al) or the like is used.

[0018]

As described above, according to the semiconductor light emitting device of the present invention, the end portions in the <010> direction of one conductivity type semiconductor layer are partially exposed alternately for each adjacent one conductivity type semiconductor layer. As described above, a semiconductor layer of opposite conductivity type is formed on a semiconductor layer of one conductivity type, and one semiconductor layer of the same conductivity type exposed at the same end side is connected to the same common electrode and is connected to a different common electrode. Since each of the adjacent adjacent upper conductivity type semiconductor layers is connected to the same individual electrode, the island-shaped semiconductor layers can be arranged without a gap in the arrangement direction, thereby achieving high definition of the light emitting element. You can In addition, current flows from one corner of the island-shaped semiconductor layer to the opposite corner, and the emitted light is reflected by the wall surface of the island-shaped semiconductor layer and guided to the central portion, improving the light extraction efficiency and increasing the brightness. It emits light.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of a semiconductor light emitting device according to the present invention.

FIG. 2 is an enlarged view showing a main part of a semiconductor light emitting device according to the present invention, in which (a) is a plan view and (b) is a sectional view.

FIG. 3 is a diagram showing a conventional semiconductor light emitting device.

4 is a cross-sectional view taken along the line AA of FIG.

[Explanation of reference numerals] 1 ... Single crystal substrate, 2 ... One conductivity type semiconductor layer, 3 ...
...... Reverse conductivity type semiconductor layer, 4 ......... Individual electrodes, 5 ...... Common electrode, 6 ... Island-like semiconductor layer, 7 ...

Continuation of front page (56) Reference JP-A-9-45955 (JP, A) JP-A-4-107886 (JP, A) JP-A-4-294591 (JP, A) JP-A-61-285775 (JP , A) JP 4-336260 (JP, A) JP 9-213991 (JP, A) JP 9-237915 (JP, A) JP 10-181077 (JP, A) 61-102061 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 33/00

Claims (3)

(57) [Claims] 1. An island-shaped semiconductor layer comprising a semiconductor layer of one conductivity type and a semiconductor layer of opposite conductivity type is formed on a single crystal substrate in a plurality of rows in the <001> direction on the single crystal substrate, and the island-shaped semiconductor is formed. The side wall portion of the layer has a <011> direction of the single crystal substrate and a <0-1
1> direction, the common electrode is connected to one end side of the one conductivity type semiconductor layer, and the individual electrode is connected to the other end side of the opposite conductivity type semiconductor layer. In the semiconductor light emitting device, in the one conductivity type semiconductor layer,
The opposite conductivity type semiconductor layer is formed on the one conductivity type semiconductor layer such that the end part on the 010> direction side is alternately exposed for every adjacent one conductivity type semiconductor layer, and the same end part is exposed. One conductive type semiconductor layer is connected to the same common electrode,
A semiconductor light-emitting device characterized in that adjacent opposite conductivity type semiconductor layers on one conductivity type semiconductor layer connected to different common electrodes are connected to the same individual electrode. 2. The semiconductor light emitting device according to claim 1, wherein one conductive type semiconductor layer under the opposite conductive type semiconductor layer connected to the same individual electrode is continuously formed. 3. The semiconductor light emitting device according to claim 1, wherein adjacent ends of the island-shaped semiconductor layers partially overlap each other in the arrangement direction of the island-shaped semiconductor layers.