JP4587521B2 - 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 junction-up type semiconductor light emitting device in which a semiconductor junction is formed on the top in order to extract light from the upper surface.
[0002]
[Background Art and Problems to be Solved by the Invention]
A conventional junction-up type semiconductor light emitting device is shown in FIG. A conventional junction-up type semiconductor light emitting device has a carrier injection layer 2 made of n-type AlGaAs, an active layer 3 made of p-type AlGaAs, a p-type AlGaAs, etc. on a substrate 1 made of n-type GaAs. And a p-type contact layer 5 and a p-side electrode 6 connected to the p-type contact layer 5, and an n-side electrode 7 on the back surface of the substrate 1. It has become.
[0003]
However, in the conventional AlGaAs junction-up type semiconductor light emitting device, since the substrate 1 and the electrode 7 are brought into ohmic contact, the substrate 1 is compared with an n-type impurity made of, for example, silicon of about 1 × 10 ¹⁸ atoms / cm ^3. It is added to a high concentration.
[0004]
Incidentally, the light λa emitted from the active layer 3 is emitted not only to the front surface side of the light emitting element but also to the back surface side thereof. As shown in FIG. 3, the light λa radiated to the back surface side of the light emitting element is not absorbed by the carrier injection layer 2 made of n-type AlGaAs having a large band gap, and reaches the substrate 1 made of GaAs having a small band gap. To reach. The light λa that has reached the GaAs substrate 1 having a high impurity concentration excites carriers in the substrate 1 and emits light λb having a wavelength different from that of the light λa corresponding to the band gap.
[0005]
However, since GaAs constituting the substrate 1 has a characteristic that the optical activity increases remarkably when the impurity concentration is increased, the secondary emission intensity is strong, and as a result, the emission spectrum of the light emitting element has the original light λa. In addition to this, there is a problem that it has a light λb which is a sub-peak, which becomes noise with respect to the light λa of the main peak.
[0006]
The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide a semiconductor light emitting device that solves the conventional problem of generating sub-peak noise in the emission spectrum of the light emitting device. And
[0007]
[Means for Solving the Problems]
In order to achieve the above object, in a semiconductor light emitting device according to the present invention, a carrier injection layer exhibiting one conductivity type, an active layer exhibiting a reverse conductivity type, and a cladding layer are sequentially formed on a semiconductor substrate exhibiting one conductivity type. In a semiconductor light emitting device formed by stacking and providing electrodes on the back side and the cladding layer of the semiconductor substrate, a light absorption layer having a smaller band gap than the active layer is provided below the carrier injection layer. It is characterized by.
[0008]
In the semiconductor light-emitting element, the carrier injection layer, the active layer, and the cladding layer is composed of AlGaAs or GaAs, the light absorbing layer is Ri consists InGaAs, the semiconductor substrate is characterized in that it consists of GaAs. Furthermore, in the semiconductor light emitting device according to the present invention, a carrier injection layer exhibiting one conductivity type, an active layer exhibiting a reverse conductivity type, and a cladding layer are sequentially stacked on a semiconductor substrate exhibiting one conductivity type, In the semiconductor light emitting device in which electrodes are provided on the back surface side and the clad layer of the semiconductor substrate, a buffer layer and a light absorption layer having a band gap smaller than that of the active layer are sequentially provided from the substrate side below the carrier injection layer. The carrier injection layer, the active layer, and the cladding layer are made of AlGaAs, the light absorption layer is made of InGaAs, and the buffer layer is made of GaAs.
[0009]
In the semiconductor light emitting device, the thickness of the light absorption layer is preferably 0.05 to 0.2 μm.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view showing an embodiment of a semiconductor light emitting device according to the present invention. Here, a red AlGaAs light emitting diode will be described as an example. In FIG. 1, 8 is a semiconductor substrate, 9 is a buffer layer, 10 is a light absorption layer, 11 is a carrier injection layer, 12 is an active layer, 13 is a cladding layer, 14 is a contact layer, and 15 and 16 are electrodes.
[0011]
The semiconductor substrate 8 contains about 1 × 10 ¹⁷ to 10 ¹⁹ atoms / cm ³ of one conductivity type impurity, a single crystal semiconductor substrate such as silicon (Si), gallium arsenide (GaAs), or indium phosphorus (InP), sapphire It consists of a single crystal insulating substrate such as (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 buffer layer 9 is made of gallium arsenide (GaAs) or the like, contains about 1 × 10 ¹⁷ to 10 ¹⁹ atoms / cm ³ of one conductivity type impurity such as Si, and is misfit based on lattice mismatch between the substrate 8 and the semiconductor layer. In order to prevent or reduce dislocation, it is formed to a thickness of about 1 to 4 μm.
[0013]
The light absorption layer 10 is made of indium gallium arsenide (InGaAs) or the like and contains about 1 × 10 ¹⁷ to 10 ¹⁹ atoms / cm ³ of one conductivity type impurity such as Si and is formed to a thickness of 0.05 to 0.2 μm. . Since the light absorption layer 10 is sandwiched between the buffer layer 9 made of GaAs and the clad layer 11 made of aluminum gallium arsenide (AlGaAs), the optical absorption layer 10 has a stress inside due to lattice mismatch and becomes a film having low optical activity. Yes.
[0014]
When the light absorption layer 10 having a small optical activity and a band gap smaller than that of an active layer to be described later is provided, light emitted to the substrate 8 side is absorbed without secondary light emission.
[0015]
When the thickness of the light absorption layer 10 is 0.05 μm or less, the reflection effect is small, and when it is 0.2 μm or more, the optical activity becomes strong and secondary light emission is facilitated. Therefore, it is desirable to form this light absorption layer 10 in a thickness of 0.05 to 0.2 μm.
[0016]
The carrier injection layer 11 exhibiting one conductivity type is formed of aluminum gallium arsenide (AlGaAs) or the like, contains about 1 × 10 ¹⁶ to 10 ¹⁹ atoms / cm ³ of one conductivity type semiconductor impurity such as silicon, and is 0.2 to It has a thickness of about 4 μm.
[0017]
The active layer 12 having the reverse conductivity type is formed of aluminum gallium arsenide (AlGaAs) or the like, and contains about 1 × 10 ¹⁶ to 10 ²¹ atoms / cm ³ of a reverse conductivity type semiconductor impurity such as zinc (Zn). It has a thickness of about 1 to 4 μm.
[0018]
The clad layer 13 having the reverse conductivity type is formed of aluminum gallium arsenide (AlGaAs), and contains about 1 × 10 ¹⁶ to 10 ²¹ atoms / cm ³ of a reverse conductivity type semiconductor impurity such as zinc (Zn). It has a thickness of about 4 μm. Note that the mixed crystal ratios of aluminum arsenide (AlAs) and gallium arsenide (GaAs) in the active layer 12 and the cladding layer 13 are made different in consideration of the carrier confinement effect and the light transmittance.
[0019]
The ohmic contact layer 14 is formed of gallium arsenide (GaAs) or the like, contains about 1 × 10 ¹⁹ to 10 ²⁰ atoms / cm ³ of a reverse conductivity type semiconductor impurity such as zinc (Zn), and has a thickness of about 0.01 to 1 μm. Have
[0020]
Next, a method for manufacturing such a semiconductor light emitting device will be described. First, the substrate 8 is heated to 700 to 1000 ° C. in an atmosphere of hydrogen (H ₂ ) and arsine gas (AsH ₃ ) by MOCVD, and the oxide on the surface of the substrate 8 is removed.
[0021]
Next, trimethyl gallium (hereinafter TMG), arsine gas (AsH ₃ ), and silane gas (SiH ₄ ) are supplied as dopant gases at a substrate temperature of 400 to 700 ° C. to form the buffer layer 9 with a thickness of about 1 to 4 μm.
[0022]
A light absorption layer 10 is formed to a thickness of about 0.05 to 0.2 μm using TMG, trimethylindium (hereinafter TMI), arsine gas (AsH ₃ ), and silane gas (SiH ₄ ) as dopant gases. To do.
[0023]
Thereafter, the carrier injection layer 11 of one conductivity type is formed using silane gas (SiH ₄ ) as a dopant gas. An active layer 12, a cladding layer 13, and an ohmic contact layer 14 are sequentially formed thereon using dimethyl zinc (hereinafter referred to as DMZ) as a dopant gas.
[0024]
After the semiconductor layers 9 to 14 are grown in this way, a mesa structure is formed using a sulfuric acid hydrogen peroxide-based etchant. Thereafter, the electrodes 15 and 16 are formed of gold / germanium (AuGe) or the like by vapor deposition or sputtering.
[0025]
【The invention's effect】
As described above, in the semiconductor light emitting device according to the present invention, a carrier injection layer exhibiting one conductivity type, an active layer exhibiting a reverse conductivity type, and a cladding layer are sequentially stacked on a semiconductor substrate exhibiting one conductivity type. Since the electrode is provided on the back side and the cladding layer of the semiconductor substrate and the light absorption layer is provided below the carrier injection layer, the light emitted from the active layer and emitted to the back side of the substrate is generated. Since the light absorption layer does not emit secondary light but is absorbed by the light absorption layer, it is possible to prevent generation of reflected light of sub-peaks and to reduce noise with respect to light of the main peak.
[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 cross-sectional view showing a conventional semiconductor light emitting device.
FIG. 3 is a diagram showing a band diagram in a bias state of a conventional semiconductor light emitting device.
[Explanation of symbols]
8: Substrate, 9: Buffer layer, 10: Light absorption layer, 11: Carrier injection layer, 12: Active layer, 13: Cladding layer, 14: Contact layer, 15, 16: Electrode

Claims (3)

On a semiconductor substrate exhibiting one conductivity type, a carrier injection layer exhibiting one conductivity type, an active layer exhibiting a reverse conductivity type, and a cladding layer are sequentially stacked, and formed on the back surface side of the semiconductor substrate and the cladding layer. In the semiconductor light emitting device provided with the electrode, a light absorption layer having a band gap smaller than the active layer is provided below the carrier injection layer, the carrier injection layer, the active layer, and the cladding layer are made of AlGaAs, and the light An absorption layer is made of InGaAs, and the semiconductor substrate is made of GaAs . On a semiconductor substrate exhibiting one conductivity type, a carrier injection layer exhibiting one conductivity type, an active layer exhibiting a reverse conductivity type, and a cladding layer are sequentially stacked, and formed on the back surface side of the semiconductor substrate and the cladding layer. In the semiconductor light emitting device provided with an electrode, a buffer layer and a light absorption layer having a band gap smaller than that of the active layer are sequentially provided below the carrier injection layer from the substrate side, and the carrier injection layer, the active layer, and A semiconductor light emitting device, wherein a cladding layer is made of AlGaAs, the light absorption layer is made of InGaAs, and the buffer layer is made of GaAs.   The semiconductor light emitting element according to claim 1, wherein the light absorption layer has a thickness of 0.05 to 0.2 μm.

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