JP3158002B2 - 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 light source for a photosensitive drum for a page printer.

[0002]

2. Description of the Related Art The structure of a conventional semiconductor light emitting device is shown in FIG. In FIG. 4, reference numeral 1 denotes a single crystal semiconductor substrate made of, for example, silicon or gallium arsenide containing an n-type semiconductor impurity; 2, a buffer layer made of, for example, a gallium arsenide layer containing an n-type semiconductor impurity; An electron injection layer made of, for example, aluminum gallium arsenide containing semiconductor impurities, 4 is a light emitting layer made of, for example, aluminum gallium arsenide containing p-type semiconductor impurities, and 5 is made of, for example, aluminum gallium arsenide containing p-type semiconductor impurities. An electron confinement layer, 6 is an ohmic contact layer made of, for example, gallium arsenide containing a p-type semiconductor impurity, 7 is a protective layer made of a silicon nitride film or the like, 8 is a common electrode provided on the back surface side of the single crystal semiconductor substrate 1 , 9 are individual electrodes provided on the ohmic contact layer 6.

With the above-described structure, when a current flows from the individual electrode 9 to the common electrode 8 (in the forward direction), the light emitting layer 4
Are injected with electrons and light is generated by radiative recombination with majority carriers.

The electron injection layer 3, the light emitting layer 4, and the electron confinement layer 5 are all made of aluminum gallium arsenide (A
1GaAs). In this case, an aluminum gallium arsenide film (Al _x Ga _{1 -x} As) having the same mixed crystal ratio is used for the electron injection layer 3 and the electron confinement layer 5, and the light emitting layer 4 has a different mixed crystal ratio from these layers. Aluminum gallium arsenide film (Al _y Ga _1-y As) is used.

[0005] In the above-described semiconductor light emitting device, a buffer layer 2, an electron injection layer 3, a light emitting layer 4, and an electron confinement layer 5 are formed on a semiconductor substrate 1 by MOCVD (metal organic chemical vapor deposition).
After sequentially forming each semiconductor layer to become the ohmic contact layer 6, the ohmic contact layer 6 is patterned into a predetermined shape, and the buffer layer 2, the electron injection layer 3, the light emitting layer 4, and the electron confinement layer 5 are sequentially formed into the predetermined shape. The individual electrodes 9 are formed by mesa etching, followed by forming a passivation film 7 made of a silicon nitride film or the like by a CVD method or the like, forming a contact hole 7a by etching, further forming a metal thin film by a vapor deposition method or the like, and patterning. Had formed.

[0006]

However, in this conventional semiconductor light emitting device, the buffer layer 2, the electron injection layer 3, the light emitting layer 4, the electron confinement layer 5, and the ohmic contact layer 6 are sequentially formed by MOCVD or the like. Later, each of these layers is etched into an island shape, and the ohmic contact layer 6 is further etched.
Since the passivation film 7 is formed by the CVD method or the like after patterning into a predetermined shape, there are many photolithography steps, the manufacturing process becomes complicated, and the electron confinement layer 5 is oxidized. . When the electron confinement layer 5 is oxidized, aluminum oxide is generated on the surface of the electron confinement layer 5 and on the exposed portion at the end of the light emitting element, which induces a leak current and causes degradation of light emission.

In the conventional semiconductor light emitting device, the buffer layer 2, the electron injection layer 3, the light emitting layer 4, and the electron confinement layer 5
Is formed by MOCVD or the like, and then is mesa-etched in an island shape, so that there is a problem that an etching area is large, a large amount of etching waste liquid is generated, and the processing becomes large.

Furthermore, in the conventional semiconductor light emitting device, there is no layer having a small band gap for absorbing the light emitted from the light emitting layer 4 above the light emitting layer 4, so that the light emission amount of the light emitting device cannot be adjusted. there were. That is, in a page printer of a low-speed machine, it is not necessary to use a light emitting device having a high light emission intensity, and it is desirable that the light emission intensity can be ranked by use in a design before production.

[0009]

SUMMARY OF THE INVENTION A semiconductor light emitting device according to the present invention has been invented in view of the problems of such a conventional device.
An object of the present invention is to provide a semiconductor light emitting device in which a complicated manufacturing process and oxidation of an electron confinement layer during the manufacturing process are eliminated.

It is another object of the present invention to provide a semiconductor light emitting device which eliminates an increase in an etching area.

Further, the semiconductor light-emitting device according to the present invention comprises:
It is an object of the present invention to provide a semiconductor light emitting device capable of easily adjusting a light emission amount.

[0012]

In order to achieve the above object, in a semiconductor light emitting device according to the present invention, a buffer layer, an electron injection layer, a light emitting layer, and a semiconductor substrate provided with one electrode are provided.
In a semiconductor light emitting device in which an electron confinement layer, an ohmic contact layer, a protective layer and the other electrode are sequentially formed,
The protective layer is made of the same Ga as the ohmic contact layer.
The protective layer was made to have a higher resistance than the ohmic contact layer without containing semiconductor impurities in the protective layer, and the protective layer was provided with a through-hole for extracting light emitted from the light emitting layer.

[0013]

With the above construction, the buffer layer, the electron injection layer, the light emitting layer, the electron confinement layer, the ohmic contact layer, and the protective layer can be manufactured by a consistent line such as the MOCVD method, thereby simplifying the manufacturing process. Also, oxidation of the electron confinement layer can be prevented.

Further, only the steps of forming the through-holes of the protective layer 7 and patterning the other electrode are photolithography steps, and the manufacturing process is simplified from this point as well.

In addition, among the buffer layer, the electron injection layer, the light emitting layer, the electron confinement layer, the ohmic contact layer, and the protective layer, only the through hole of the protective layer is removed by etching, and the etching amount is small. In addition, it becomes easy to treat the waste liquid for etching.

Furthermore, in the present invention, since light is extracted through the ohmic contact layer, the light extraction amount (the light emission amount of the light emitting device) can be adjusted by adjusting the thickness of the ohmic contact layer.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a semiconductor light emitting device according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a plan view showing an embodiment of a semiconductor light emitting device according to the present invention, FIG. 2 is a cross-sectional view taken along the line AA of FIG. 1, 1 is a semiconductor substrate containing an n-type semiconductor impurity, and 2 is n Buffer layer made of gallium arsenide or the like containing n-type semiconductor impurities, 3 is an electron injection layer made of aluminum gallium arsenide or the like containing n-type semiconductor impurities, 4 is a light emitting layer made of aluminum gallium arsenide or the like containing p-type semiconductor impurities Reference numeral 5 denotes an electron confinement layer made of aluminum gallium arsenide or the like containing a p-type semiconductor impurity, 6 denotes an ohmic contact layer made of gallium arsenide or the like containing a p-type semiconductor impurity, 7
Is a gallium As layer containing no semiconductor impurities.

The semiconductor substrate 1 used in the semiconductor light emitting device according to the present invention has a 2 ° angle from the (100) plane to the (011) plane.
A single crystal semiconductor substrate which is formed of a single crystal silicon substrate or a single crystal gallium arsenide substrate cut off and contains a donor made of antimony (Sb) or the like at about 10 ¹⁷ atm / cm ³ is used.

On the n-type semiconductor substrate 1, a buffer layer 2 containing an n-type impurity is formed. The buffer layer 2 is made of gallium arsenide or the like, and is made of silicon (Si).
About 10 ¹⁸ atm / cm ³ . When the semiconductor substrate 1 is formed of, for example, a single crystal silicon substrate, the buffer layer 2 suitably employs a two-step growth method or a thermal cycle method in order to prevent dislocation due to a difference in lattice constant between silicon and gallium arsenide. It is formed to a thickness of about 1 to 3 μm by MOCVD. That is, MOCV
After once heating the inside of the D apparatus at 900 to 1000 ° C.,
A GaAs film is grown by lowering the temperature to 00 to 450 ° C., and a GaAs film is grown by raising the temperature to 600 to 650 ° C. (two-step growth). Then, the temperature is raised and lowered at 300 to 900 ° C. (thermal cycle method). An internal stress due to a difference in expansion coefficient is generated, and dislocation due to a difference in lattice constant between the silicon substrate 1 and the GaAs layer 2 is reduced.

On the buffer layer 2 containing the n-type impurity, an electron injection layer 3 containing the n-type impurity is formed. The electron injection layer 3 containing this n-type impurity is made of, for example, an Al _x Ga _{1 -x} As layer, and is made of silicon (S
It contains about 10 ¹⁷ atm / cm ^{3 of the} donor composed of i) and the like.

On the electron injection layer 3, a light emitting layer 4 is formed. The light emitting layer 4 is made of Al _x Ga _{1 -x} As or the like, and acceptors made of zinc (Zn) or the like have a density of 10 ¹⁷ a.
It contains about tm / cm ³ . The mixed crystal ratio x of Al _x Ga _{1 -x} As in the electron injection layer 3 is 0.3 to 0.4.
, And Al _y Ga _1-y As in the light emitting layer 4.
Is set to about 0.6 to 0.7. In any case, the mixed crystal ratio of these layers is set such that the electron injection layer 3 and the electron confinement layer 5 having a large band gap are located on both sides of the light emitting layer 4 made of Al _y Ga _1-y As containing an n-type impurity. Set.

An electron confinement layer 5 made of Al _x Ga _{1 -x} As containing a p-type semiconductor impurity is formed on the light emitting layer 4.
Are formed. The electron confinement layer 5 is formed to a thickness of about 1 μm, and the mixed crystal ratio x is 0.3 to 0.3 as described above.
It is set to about 0.4.

On the electron confinement layer 5, an ohmic contact layer 6 made of GaAs or the like containing a large amount of p-type impurities is formed. The ohmic contact layer 6 is made of an acceptor made of zinc (Zn) or the like at 10 ²⁰ a.
It contains about tm / cm ³ and is formed to a thickness of about 0.1 to 1.0 μm.

On the ohmic contact 6, a high resistance protective layer 7 is formed. This protective layer 7 is made of, for example, a GaAs layer, like the ohmic contact layer 6, and basically does not contain semiconductor impurities. That is,
In the vicinity of the ohmic contact layer 6, semiconductor impurities mixed from the ohmic contact layer 6 may be contained, but are not intentionally contained. That is, it is for partitioning an element region as a light emitting element. Incidentally, the GaAs film containing no semiconductor impurities is 26 to
It has electrical insulation of about 63 × 10 ⁷ Ω · cm.

FIG. 3 shows the thickness of the gallium As film and 10 μW
2 shows the relationship between the light absorptivity of the light emitting devices. The thickness of gallium arsenide is 0.
At 15 μm, the light absorptance is 12%, whereas
When the film thickness becomes 1.5 μm, the light absorption becomes 100%.
Therefore, when the thickness of the gallium arsenide film (the total of the ohmic contact layer 6 and the protective layer 7) becomes 1.5 μm or more, the light emitted from the light emitting layer 4 is completely blocked. On the other hand, if the thickness of the ohmic contact layer 6 is set to 0.15 μm,
About 90% of the light emitted from the light emitting layer 4 is extracted.

An individual electrode (the other electrode) 9 is formed on the ohmic contact layer 6 at the portion of the through-hole 7a of the protective layer 7, and the individual electrode 9 is made of gold (Au) / chromium (Cr). And is formed to a thickness of about 5000 ° by a vapor deposition method or the like.

A common electrode (one electrode) 8 is formed on the back surface of the semiconductor substrate 1. The common electrode 8 is made of aluminum or aluminum silicide (AlSi), and has a thickness of about 5000.degree. Formed.

The semiconductor light emitting device formed as described above,
A current is caused to flow between the individual electrodes 9 and the common electrode 8 to generate carriers in the n-type electron injection layer 3 and the p-type light-emitting layer 4 and recombine at the interface to emit light.

In the semiconductor light emitting device as described above, a buffer layer 2 made of gallium arsenide, an electron injection layer 3 made of an n-type aluminum gallium arsenide film, etc., a p-type aluminum gallium arsenide film An electron confinement layer 5 made of, for example, an ohmic contact layer 6 made of a gallium arsenide film or the like, and a protective layer 7 made of a gallium arsenide film or the like are sequentially formed by MOCVD or the like. Next, the through-holes 7a are formed in the protective layer 7 so as to be arranged in a row when viewed in plan. The through hole 7a is for taking out the light emitted from the light emitting layer 4 to the outside, and has the shape of the light emitting element itself. Specifically, it is formed with a size of about 50 × 50 μm and a pitch of about 60 μm. The through holes 7a are formed by etching predetermined portions of the protective layer 7. Next, a common electrode 8 is formed on the back side of the semiconductor substrate 1, and an individual electrode 9 is formed on the back side by patterning. In the manufacturing process of such a semiconductor light emitting device, only two processes of forming the through-holes 7a of the protective layer 7 and patterning the individual electrodes 9 are photolithography processes.

[0030]

As described above, according to the semiconductor light emitting device of the present invention, the buffer layer, the electron injection layer, the light emitting layer, the electron confinement layer, the ohmic contact layer and the protective layer are formed by MO.
It can be manufactured in a consistent line such as a CVD method, so that the manufacturing process is simplified and oxidation of the electron confinement layer can be prevented. Further, only the step of forming the through-hole portion of the protective layer 7 and the step of patterning the other electrode are photolithography steps, and the manufacturing process is simplified from this point as well. Further, among the buffer layer, the electron injection layer, the light emitting layer, the electron confinement layer, the ohmic contact layer, and the protective layer, only the through-hole portion of the protective layer is removed by etching, and the etching amount is small. The disposal of waste liquid is also facilitated.
Furthermore, since light is extracted through the ohmic contact layer, the light extraction amount (light emission amount) can be adjusted by adjusting the thickness of the ohmic contact layer.

[Brief description of the drawings]

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

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

FIG. 3 is a diagram showing a relationship between a thickness of an ohmic contact layer and a light absorption rate.

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

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor substrate, 2 ... Buffer layer, 3 ... Electron injection layer, 4 ... Light emitting layer, 5 ... Electron confinement layer,
6 ... ohmic contact layer, 7 ... protective layer, 7
a: through-hole, 8: common electrode, 9: individual electrode

Claims (1)

(57) [Claims] 1. A semiconductor light emitting device in which a buffer layer, an electron injection layer, a light emitting layer, an electron confinement layer, an ohmic contact layer, a protective layer, and the other electrode are sequentially formed on a semiconductor substrate provided with one electrode. A layer is formed of the same GaAs as that of the ohmic contact layer. The protective layer does not contain semiconductor impurities to have a higher resistance than the ohmic contact layer, and the protective layer transmits light emitted from the light emitting layer. A semiconductor light emitting device comprising a hole.