JP3270799B2 - 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,
In particular, the present invention relates to a semiconductor light emitting device used as an exposure source of a photosensitive drum for a page printer.

[0002]

2. Description of the Related Art A conventional semiconductor light emitting device is shown in FIGS.
Shown in FIG. 5 is a sectional view taken along line AA of FIG. 4 and 5, 21 is a substrate, 22 is an island-shaped semiconductor layer,
23 is an individual electrode and 24 is a common electrode.

The substrate 21 is made of, for example, a single crystal semiconductor substrate such as silicon (Si) or gallium arsenide (GaAs).

The island-shaped semiconductor layer 22 is made of a compound semiconductor such as gallium arsenide or aluminum gallium arsenide, and includes a layer 22a containing impurities of the opposite conductivity type and a layer 22b containing impurities of one conductivity type. A semiconductor junction is formed at the interface between the layer 22a containing the opposite conductivity type impurity and the layer 22b containing the one conductivity type impurity. The island-shaped semiconductor layer 22 is formed in an island shape after a single-crystal semiconductor layer is formed by, for example, MOCVD or MBE.

A protective film 25 made of, for example, a silicon nitride film or the like is formed on the surface of the island-shaped semiconductor layer 22, and the surface of the protective film 25 is formed of, for example, gold (Au).
An individual electrode 23 is formed. The individual electrodes 23 are alternately provided from the upper surface portion of the layer 22 a containing the impurity of the opposite conductivity type of the island-like semiconductor layer 22 to the vicinity of the end surface of the substrate 21 from the adjacent island-like semiconductor layer 22 via the wall surface portion. It is formed to extend. A common electrode 24 made of gold (Au) or the like is formed on almost the entire back surface of the substrate 21.

Each light emitting element (light emitting diode) is composed of the island-shaped semiconductor layer 22, the individual electrode 23 and the common electrode 24, and is formed on the substrate 21 so as to be arranged 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. The individual electrode 23 is connected to an external circuit at a wide portion by a wire bonding method or the like.

In such a semiconductor light emitting device, as shown in FIG. 5, when a current flows in a forward direction from, for example, the individual electrode 23 to the common electrode 24, electrons are contained in the layer 22a containing the impurity of the opposite conductivity type. Holes are implanted into the layer 22b containing the impurity of the opposite conductivity type. Some of these minority carriers emit light by radiative recombination with majority carriers. In addition, by selecting one of the light emitting elements formed in a row to emit light, the light emitting element is used as a light source for static elimination of a photosensitive drum for a page printer, for example.

The common electrode 24 shown in FIG.
It may be provided on one surface side.

[0009]

However, in this conventional semiconductor light emitting device, the semiconductor layer 22b containing one conductivity type impurity is connected via the substrate 21 to the common electrode 24 formed on the back side of the substrate 21. However, since the semiconductor layer 22 a containing the impurity of the opposite conductivity type is individually connected to the individual electrode 23, when the light emitting element is refined, the formation density of the individual electrode 23 is increased, and the external density is accordingly increased. There is a problem that the number of connection points with the circuit increases and the workability of wire bonding deteriorates. For example, 30
In the case of a semiconductor light emitting device of 0 dpi (dot per inch), the arrangement pitch of the island-shaped semiconductor layers 22 is 84.6 μm, and in the case of a semiconductor light emitting device of 600 dpi, the arrangement pitch of the island-shaped semiconductor layers 22 is 42.3 μm. There is a problem that the individual electrode 23 has to be narrower than 300 dpi, and the workability of wire bonding is deteriorated.

Further, if the number of individual electrodes 23 increases, the number of wire bonding locations increases accordingly, and there is a problem that the wire bonding operation requires a long time.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and eliminates an increase in the formation density of individual electrodes connected to a light emitting element, and has been developed for wire bonding. It is an object of the present invention to provide a semiconductor light emitting device which eliminates a long time.

[0012]

In order to achieve the above object, according to the first aspect of the present invention, an island-shaped semiconductor layer comprising a semiconductor layer of one conductivity type and a semiconductor layer of the opposite conductivity type is provided on a substrate. A semiconductor light-emitting device comprising a plurality of light-emitting diodes provided with a common electrode connected to the one-conductivity-type semiconductor layer and provided with an individual electrode connected to the opposite-conductivity-type semiconductor layer. The opposite conductivity type semiconductor layer is provided in a smaller area than the one conductivity type semiconductor layer, and is connected to the one conductivity type semiconductor layer in each of a plurality of groups divided from the one conductivity type semiconductor layer to the substrate. An electrode was provided, and individual electrodes connected to a plurality of opposite conductivity type semiconductor layers belonging to different groups were provided from the opposite conductivity type semiconductor layer to the substrate.

[0013]

In the semiconductor light emitting device according to the present invention, the density of the individual electrodes connected to the light emitting element is reduced and the number of the individual electrodes is reduced, so that the wire bonding operation can be performed in a short time.

[0014]

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a view showing one embodiment of a semiconductor light emitting device according to the present invention, and FIG. 2 is a sectional view taken along line AA of FIG. 1 and 2, 1 is a substrate, 2 is an island-shaped semiconductor layer, 3 is an individual electrode, and 4 is a common electrode.

The substrate 1 is made of, for example, a single crystal semiconductor substrate such as silicon (Si) or gallium arsenide (GaAs).

The island-shaped semiconductor layer 2 comprises a layer 2a made of a compound semiconductor film such as gallium arsenide or aluminum gallium arsenide (GaAlAs) and containing a reverse conductivity type impurity and a layer 2b containing one conductivity type impurity. A semiconductor junction is formed at the interface between the layer 2a containing the impurity of the opposite conductivity type and the layer 2b containing the impurity of the one conductivity type. The island-shaped semiconductor layer 2 is formed in an island shape after forming a single-crystal semiconductor layer by, for example, MOCVD or MBE. That is,
First, the natural oxide film of the substrate 1 is removed at a high temperature of 800 ° C. to 1000 ° C. Next, after growing amorphous gallium arsenide serving as a nucleus at a low temperature of 450 ° C. or less by MOCVD or MBE to a thickness of about 0.1 to 2 μm,
The temperature is raised from 700C to 700C, and the amorphous gallium arsenide is recrystallized to grow a gallium arsenide single crystal (two-step growth method). Next, post-annealing such as repeating annealing at a high temperature of 750 ° C. to 1000 ° C. and rapid cooling to a low temperature of 600 ° C. or less several times (temperature cycle method) is performed. In this case, trimethylgallium [(CH ₃ ) ₃ Ga] or the like is used as a raw material of gallium, arsine [AlH ₃ ] or the like is used as a raw material of arsenic, and trimethyl aluminum [(CH ₃ ) is used as a raw material of aluminum. ₃ A
l] etc. are used.

The layer 2a containing the impurity of the opposite conductivity type
Is, for example Zn, 10 a semiconductor impurity element such as Cd ¹⁶
The layer 2b containing about 10 to 10 ¹⁹ cm ^{-3 and} containing one conductivity type impurity contains about 10 ¹⁶ to 10 ¹⁹ cm ^{-3 of} an impurity element such as S, Se, Te, Ge, and Si.

The layer 2 containing the impurity of the opposite conductivity type is
The layer 2b containing a or one conductivity type impurity may be formed of a plurality of layers having different compound crystal ratios. The layer 2a containing the impurity of the opposite conductivity type has a smaller area than the layer 2b containing the impurity of the one conductivity type. That is, the layer 2b containing the one-conductivity-type impurity is also formed so that its surface is partially exposed.

On the surface of the island-shaped semiconductor layer 2, a protective film 5 made of, for example, a silicon nitride film is formed.
Common electrodes 4a and 4b made of, for example, gold (Au) so as to extend from the exposed portion of layer 2b containing one conductivity type impurity in island-shaped semiconductor layer 2 to the vicinity of the end face of substrate 1.
Are formed. The island-shaped semiconductor layers 2 are alternately connected to the common electrodes 4a and 4b alternately. That is, the island-shaped semiconductor layer 2 is divided into two groups, and the common electrodes 4a and 4b are provided for each group.

The individual electrode 3 is formed so as to extend from the surface of the layer 2a containing the impurity of the opposite conductivity type in the island-shaped semiconductor layer 2 to the vicinity of the opposite end face via the opposite wall face. Have been. One individual electrode 3 is formed for each adjacent island-shaped semiconductor layer 2. That is, one individual electrode 3 is provided for each semiconductor light emitting element belonging to a different group. The wide portion of the individual electrode 3 becomes an electrode pad for performing wire bonding for connection to an external circuit. By selecting a combination of the individual electrode 3 and the common electrodes 4a and 4b, individual semiconductor light emitting elements can be selected to emit light.

FIG. 3 is a circuit diagram showing one embodiment of the semiconductor light emitting device according to the present invention. 3, reference numeral 11 denotes a semiconductor light emitting element, 12 denotes a switching transistor, and 13 denotes a switching transistor.
Is a gate circuit, 14 is a latch circuit, and 15 is a shift register. In the driving circuit of this semiconductor light emitting device,
A non-emission data signal is input from DATA1 and DATA2 to the shift register 15 at the timing of the CLOCK signal, and is pulled up to the latch circuit 14 at the timing of the LATCH signal. The emission / non-emission data signal and STPB1
Alternatively, it is determined whether or not the switching transistor 12 is to be turned on by the logical product of STPB2.
A current is selectively passed to ND1 or GND2 (common electrode 4a or 4b).

In the above embodiment, a plurality of semiconductor light emitting elements 2
Are divided into two groups and connected to the two common electrodes 4a and 4b, and two semiconductor light emitting elements 2 belonging to each group are connected to each other.
Although the connection to the individual electrodes 3 has been described as a set, the plurality of semiconductor light emitting elements 2 are divided into three groups or more.
The semiconductor light emitting elements 2 may be connected to the individual electrodes 3 in sets of three or more.

[0024]

As described above, according to the semiconductor light emitting device of the first aspect, the opposite conductivity type semiconductor layer is provided on the one conductivity type semiconductor layer in a smaller area than the one conductivity type semiconductor layer. A common electrode connected to one conductive semiconductor layer is provided for each group divided into a plurality of groups from the conductive semiconductor layer to the substrate, and a plurality of reverse electrodes belonging to different groups from the reverse conductive semiconductor layer to the substrate are provided. Since the individual electrodes connected to the conductive semiconductor layer are provided, the formation density of the electrode pads is reduced,
The workability of wire bonding is improved, and the work can be performed in a short time. The island-shaped semiconductor layers can be divided into a plurality of groups and connected to a common electrode, and the individual electrodes can be connected to a plurality of islands belonging to different groups. It can be provided for each semiconductor layer.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of a semiconductor light emitting device according to the present invention.

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

FIG. 3 is an electric circuit diagram showing one embodiment of a semiconductor light emitting device according to the present invention.

FIG. 4 is an electric circuit diagram showing one embodiment of a conventional semiconductor light emitting device.

FIG. 5 is a sectional view taken along line AA in FIG.

FIG. 6 is an electric circuit diagram showing a conventional semiconductor light emitting device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Island-shaped semiconductor layer, 3 ... Individual electrode, 4 ... Common electrode

Claims (1)

(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 provided on a substrate, a common electrode is connected to the semiconductor layer of one conductivity type, and In a semiconductor light emitting device including a plurality of light emitting diodes provided by connecting individual electrodes , the opposite conductivity type semiconductor layer is provided on the one conductivity type semiconductor layer in a smaller area than the one conductivity type semiconductor layer. A common electrode connected to one conductive semiconductor layer is provided for each group divided into a plurality of groups from the conductive semiconductor layer to the substrate and belongs to different groups from the reverse conductive semiconductor layer to the substrate. Duplicate
A semiconductor light emitting device, comprising: a plurality of individual electrodes connected to opposite conductivity type semiconductor layers .