JP3623110B2 - Semiconductor light emitting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor light emitting device, and more particularly to a semiconductor light emitting device used for an exposure light source of a photosensitive drum for a page printer.
[0002]
[Prior art and problems to be solved by the invention]
A conventional semiconductor light emitting device is shown in FIGS. 3 is a cross-sectional view, and FIG. 4 is a plan view. 3 and 4, 21 is a semiconductor substrate, 22 is a one-conductivity-type semiconductor layer, 23 is a reverse-conductivity-type semiconductor layer, 24 is an individual electrode, and 25 is a common electrode.
[0003]
On the semiconductor substrate 21, a one-conductivity-type semiconductor layer 22 and a reverse-conductivity-type semiconductor layer 23 are provided so that the reverse-conductivity-type semiconductor layer 23 has a smaller area than the one-conductivity-type semiconductor layer 22. The common electrode 25 (25a, 25b) is connected to the exposed portion R of 22 and the individual electrode 24 is connected to the reverse conductivity type semiconductor layer 23. In FIG. 3, reference numeral 26 denotes a protective film made of a silicon nitride film or the like. In addition, as shown in FIG. 4, the common electrode 25 (25a, 25b) is provided in two groups so as to belong to different groups for each of the adjacent island-like semiconductor layers 22 and 23, and is connected to the adjacent island-like semiconductor layers 22 and 23. The semiconductor layers 22 and 23 are connected to the same individual electrode 24.
[0004]
In such a light emitting diode array, each light emitting diode can be made to emit light selectively by selecting a combination of the individual electrode 24 and the common electrode 25 (25a, 25b) and flowing a current.
[0005]
However, in this conventional semiconductor light emitting device, the individual electrode 24 and the common electrode 25 (25a, 25b) are provided in close proximity to each other in the exposed portion R of the one-conductivity type semiconductor layer 22. There has been a problem that short-circuiting often occurs due to burrs or dust.
[0006]
Moreover, in the conventional semiconductor light emitting device, the sidewall portion W of the reverse conductivity type semiconductor layer 23 in the exposed portion R of the island-like semiconductor layers 22 and 23 is structured to be a forward mesa. There is a problem in that light leakage occurs and the print quality deteriorates.
[0007]
The present invention has been made in view of such problems of the conventional device, and is caused by the fact that the side wall portion of the reverse conductivity type semiconductor layer in the exposed portion R of the one conductivity type semiconductor layer has a forward mesa structure. An object of the present invention is to provide a semiconductor light emitting device that eliminates short-circuiting of electrodes and deterioration of print quality.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, in the semiconductor light emitting device according to the present invention, an island-shaped one-conductivity-type semiconductor layer is provided on a substrate, and a part of the one-conductivity-type semiconductor layer is formed on the one-conductivity-type semiconductor layer. In a semiconductor light emitting device in which an opposite conductivity type semiconductor layer is provided so as to be exposed, and an electrode is connected to the exposed portion of the one conductivity type semiconductor layer and the opposite conductivity type semiconductor layer, the connection is made to the opposite conductivity type semiconductor layer In addition, the electrode to be formed is formed in a rectangular shape, and the side wall portion of the opposite conductivity type semiconductor layer in the exposed portion of the one conductivity type semiconductor layer has an inverted mesa structure, and light is reflected by the inverted mesa structure portion and extracted upward. It is characterized by that.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a sectional view showing an embodiment of a semiconductor light emitting device according to the present invention, and FIG. 2 is a plan view.
[0010]
1 and 2, 1 is a substrate, 2 is a one-conductivity-type semiconductor layer, 3 is a reverse-conductivity-type semiconductor layer, 4 is an individual electrode, 5 is a common electrode, and 6 is an insulating film.
[0011]
The substrate 1 is made of a single crystal semiconductor substrate such as silicon (Si) or gallium arsenide (GaAs) or a single crystal insulating substrate such as sapphire (Al ₂ O ₃ ). In the case of a single crystal semiconductor substrate, a substrate in which the (100) plane is turned off by 2 to 7 degrees in the <011> direction is preferably used. In the case of sapphire, a C-plane substrate is preferably used.
[0012]
The one conductivity type semiconductor layer 2 includes a buffer layer 2a, an ohmic contact layer 2b, and a light emitting layer 2c. The buffer layer 2a is formed to a thickness of about 2 to 4 μm, the ohmic contact layer 2b is formed to a thickness of about 0.1 to 1.0 μm, and the cladding layer 2c is formed to a thickness of about 0.2 to 0.4 μm. The The buffer layer 2a and the ohmic contact layer 2b are formed of gallium arsenide or the like, and the light emitting layer 2c is formed of aluminum gallium arsenide or the like. The ohmic contact layer 2b contains about 1 × 10 ¹⁸ to 10 ²² atoms / cm ³ of one conductivity type semiconductor impurity such as silicon and selenium, and the cladding layer 2c contains 1 × 10 ¹⁶ one conductivity type semiconductor impurity such as silicon and selenium. About 10 ¹⁹ atoms / cm ³ . The buffer layer 2a is provided in order to prevent misfit dislocation based on mismatch of lattice constants between the substrate 1 and the semiconductor layer, and does not need to contain semiconductor impurities.
[0013]
The reverse conductivity type semiconductor layer 3 includes a light emitting layer 3a, a second cladding layer 3b, and a second ohmic contact layer 3c. The light emitting layer 3a and the second cladding layer 3b are formed to a thickness of about 0.2 to 0.4 μm, and the ohmic contact layer 3c is formed to a thickness of about 0.01 to 0.1 μm. The light emitting layer 3a and the second cladding layer 3b are made of aluminum gallium arsenide or the like, and the second ohmic contact layer 3c is made of gallium arsenide or the like.
[0014]
The light emitting layer 3a and the second cladding layer 3b have different mixed crystal ratios of aluminum arsenide (AlAs) and gallium arsenide (GaAs) in consideration of the electron confinement effect and the light extraction effect. The light emitting layer 3a and the second cladding layer 3b contain about 1 × 10 ¹⁶ to 10 ¹⁹ reverse conductive semiconductor impurities such as zinc (Zn), and the second ohmic contact layer 3c is a reverse conductive semiconductor impurity such as zinc. About 1 × 10 ¹⁹ to 10 ²² .
[0015]
The insulating film 6 is made of silicon nitride or the like and has a thickness of about 3000 mm. The individual electrode 4 and the common electrode 5 are made of gold / chromium (Au / Cr) or the like and are formed with a thickness of about 1 μm.
[0016]
In the semiconductor light emitting device of the present invention, as shown in FIG. 2, island-like semiconductor layers 2 and 3 comprising a one-conductivity-type semiconductor layer 2 and a reverse-conductivity-type semiconductor layer 3 are arranged in a line on a substrate 1 and adjacent islands are arranged. Each of the semiconductor layers 2 and 3 is connected to the same individual electrode 4 and is connected in two groups so that the lower one conductive semiconductor layer 2 connected to the same individual electrode 4 is connected to a different common electrode 5. The By selecting an individual electrode 4 and passing an electric current, it is used as an exposure light source for a photosensitive drum for a page printer.
[0017]
In the island-like semiconductor layers 2 and 3, one opposing wall surface has a forward mesa structure and the other opposing wall surface has an inverted mesa structure because of the relationship between crystal plane orientation and etching. In the present invention, the sidewall portion W of the reverse conductivity type semiconductor layer 3 in the exposed portion R of the one conductivity type semiconductor layer 2 is formed to be a reverse mesa. That is, when performing step etching, the side wall W of the reverse conductivity type semiconductor layer 3 is formed in a reverse mesa shape using an etching solution in which GaAs has a forward mesa shape, but the <1-10> direction of AlGaAs has a reverse mesa shape. To. By making the side wall W of the reverse conductivity type semiconductor layer 3 into an inverted mesa shape, the upper portion of the individual electrode 4 on the reverse conductivity type semiconductor layer 3 and the upper portion of the one conductivity type semiconductor layer 2 can be cut.
[0018]
Further, since the side wall portion W of the reverse conductivity type semiconductor layer 3 in the exposed portion R of the one conductivity type semiconductor layer 2 is formed as a reverse mesa, the light emitted from the light emitting layers 2c and 3a is emitted from the side wall portion W. Reflected inside and irradiated upward. Accordingly, light leakage from the side wall portion Y is eliminated.
[0019]
Next, a method for manufacturing the semiconductor light emitting device as described above will be described. First, a one-conductivity-type semiconductor layer 2 and a reverse-conductivity-type semiconductor layer 3 are sequentially stacked on a single crystal substrate 1 by MOCVD or the like.
[0020]
When these semiconductor layers 2 and 3 are formed, the substrate temperature is first set to 400 to 500 ° C., an amorphous gallium arsenide film is formed to a thickness of 200 to 2000 mm, and then the substrate temperature is raised to 700 to 900 ° C. Thus, the semiconductor layers 2 and 3 having a desired thickness are formed.
[0021]
In this case, as source gases, TMG ((CH ₃ ) ₃ Ga), TEG ((C ₂ H ₅ ) ₃ Ga), arsine (AsH ₃ ), TMA ((CH ₃ ) ₃ A1), TEA ((C ₂ H ₅ ) ₃ A1) and the like are used, and silane (SiH ₄ ), hydrogen selenide (H ₂ Se), TMZ ((CH ₃ ) ₃ Zn), and the like are used as the gas for controlling the conductivity type. As the carrier gas, H ₂ or the like is used.
[0022]
Next, the semiconductor layers 2 and 3 are patterned in an island shape so that adjacent elements are electrically separated. This etching is performed by wet etching using a sulfuric acid hydrogen peroxide-based etching solution or dry etching using CC1 ₂ F ₂ gas. Further, etching is performed so that the connection portion between the one-conductivity-type semiconductor layer 2 and the common electrode 5 is exposed from the reverse-conductivity-type semiconductor layer 3. This etching is performed by wet etching using an etchant such as I ₂ : KI: HCl: H ₂ O = 2 g: 4 g: 1 cc: 100 cc.
[0023]
Next, an insulating film made of silicon nitride is formed and patterned by plasma CVD using silane gas (SiH ₄ ) and ammonia gas (NH ₃ ). Finally, chromium and gold are formed by vapor deposition or sputtering and patterned.
[0024]
【The invention's effect】
As described above, according to the semiconductor light emitting device of the present invention, the electrode connected to the reverse conductivity type semiconductor layer is formed in a rectangular shape, and the reverse conductivity type semiconductor layer in the exposed portion of the one conductivity type semiconductor layer is formed. Since the side wall portion has an inverted mesa structure and light is reflected by the inverted mesa structure portion and extracted upward, the electrode on the one-conductivity-type semiconductor layer can be cut at the inverted mesa portion. Even if they are arranged close to each other, a short circuit or the like can be effectively prevented. In addition, light leakage from the vicinity of the exposed portion of the one conductivity type semiconductor layer can be reduced, and the printing quality can be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of a semiconductor light emitting device according to the present invention.
FIG. 2 is a plan view showing an embodiment of a semiconductor light emitting device according to the present invention.
FIG. 3 is a cross-sectional view showing a conventional semiconductor light emitting device.
FIG. 4 is a plan view showing a conventional semiconductor light emitting device.
[Explanation of symbols]
1 ... substrate, 2 ... one conductivity type semiconductor layer, 3 ... reverse conductivity type semiconductor layer, 4 ... individual electrode, 5 ... common electrode, 6 ... insulation film

Claims (1)

An island-shaped one-conductivity-type semiconductor layer is provided on the substrate, and a reverse-conductivity-type semiconductor layer is provided on the one-conductivity-type semiconductor layer so that a part of the one-conductivity-type semiconductor layer is exposed. In the semiconductor light emitting device provided by connecting an electrode on the exposed portion of the layer and the reverse conductivity type semiconductor layer, the electrode connected to the reverse conductivity type semiconductor layer is formed in a rectangular shape and the one conductivity type semiconductor layer A semiconductor light emitting device characterized in that a side wall portion of the reverse conductivity type semiconductor layer in the exposed portion has a reverse mesa structure, and light is reflected by the reverse mesa structure portion and extracted upward .

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