JPH08125277A - Semiconductor device having V-groove structure - Google Patents

Abstract

PURPOSE: To form a V-grooved structure into a structure, by which a quantum fine wire, which is good in quality and has a distortion, is easily obtained, by a method wherein a groove with a section formed into a V shape is formed in a part of an epitaxially grown layer grown in a semiconductor substrate or on a semiconductor substrate, an active layer having a distortion is provided on the bottom of the groove and the active layer is buried in a clad layer. CONSTITUTION: A GaAs layer, an Al0.5 Ga0.5 As layer and a GaAs layer are formed in order on a (100) GaAs substrate by an MOCVD method. A V-shaped groove having the G face (111) on the side surfaces on both sides thereof is formed in the surface of this epitaxial substrate. Then, an In0.2 Ga0.8 As distorted active layer is formed in the V-shaped groove and moreover, an Al0.5 Ga0.5 As clad layer and a GaAs layer are formed. At this time, as an epitaxial growth is difficult on the B faces (111), the growth is not caused on the sidewalls of the V-shaped groove and a GaAs quantum fine wire is formed on the bottom of the V-shaped groove in a self alignment manner. As a sharply pointed V-shaped groove is formed in the point part of the V-shaped groove, an In0.2 Ga0.8 As thin wire is buried only in the bottom of the V-shaped groove.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, preferably a semiconductor device using the quantum effect.

[0002]

2. Description of the Related Art A semiconductor device having a quantum microstructure such as a quantum well, a quantum wire, and a quantum box is particularly preferably used as a semiconductor light emitting device, and has a low threshold current due to a quantization effect of electrons and holes. Excellent characteristics are obtained in high modulation band, high coherence characteristics, and the like. This effect is prominent when the strain less than the critical film thickness is introduced into the active layer.

As a method of forming a quantum wire, a quantum well structure is formed and then a fine photolithography method by electron beam exposure or the like and vertical etching by an ion beam are used in combination to form a wire.
A method of forming a V-shaped groove on the substrate shown in FIG. 4 and then growing a double hetero structure on the entire surface of the substrate having a groove having a V-shaped cross section (hereinafter referred to as “V groove”) is performed. There is.

[0004]

In a fine structure such as a quantum wire, a quantum effect exists even in a thick film rather than on a plane, and this fact is convenient for gaining. When an attempt is made to grow a strained active layer having a lattice mismatch rate of 1 to 2% in which a strain effect appears on a flat substrate surface, the strained active layer receives stress on the entire surface, and thus the film thickness at which dislocation begins to occur, that is, The critical film thickness is 10
Since it is only about 20 nm, it is often impossible to make the strained active layer sufficiently thick when it is used as a thin wire. However, in the former method, the side wall of the groove is largely damaged by the processing, and the quality of the fine wire is likely to be inferior. On the other hand, in the latter, the quantum wire can be selectively formed by utilizing the orientation dependence of the growth rate, but the bottom of the formed V groove is rounded depending on the composition of the portion where the V groove is to be formed. In some cases, during wet etching, an oxide film is formed on the etching surface during wet etching, it is contaminated with impurities, or the bottom of the V groove is rounded due to etching.

Therefore, there is a demand for a structure capable of easily obtaining a high quality quantum wire. In addition, improving the efficiency of semiconductor devices is also a current issue.

[0006]

The inventors of the present invention, as a result of intensive research, have found that such a problem can be solved by a specific structure, and have reached the present invention. That is, an object of the present invention is to provide a semiconductor device having a high-quality quantum wire, and an object thereof is to form a V-shaped cross section in at least a part of a semiconductor substrate or an epitaxial growth layer grown on the semiconductor substrate. A semiconductor device having a groove, in which a strained active layer is provided at the bottom of the V-shaped groove, and the active layer has a structure filled with a cladding layer, more preferably, the active layer is The semiconductor device having a quantum well structure, which has inner and outer clad layers of a V-shaped structure that are in contact with each other at the slope of the V-shaped groove, and the energy gap of the outer clad layer is the inner clad layer. Of the semiconductor device having a structure that is larger than the energy gap of the semiconductor device, the semiconductor device in which the slope of the V-shaped groove is a {111} B plane, and the groove of the V-shaped groove are vapor-phase etched. By the semiconductor device or the like which is more formed, it is readily achieved.

The present invention will be described in detail below. The structure of the semiconductor device of the present invention is III-V compound semiconductor, II-VI.
It can be suitably used for group compound semiconductors and the like. The structure of the present invention is preferably used as an electronic element utilizing the conduction of carriers in the active region, and particularly preferably used as a light emitting semiconductor device.

The structure of the semiconductor device of the present invention will be described with reference to the explanatory view of the device of FIG. 1 grown on the III-V group (100) plane GaAs substrate prepared in the embodiment. (10
The (0) plane is used because the symmetry and straightness of the V-groove affect the symmetry and straightness of the quantum well. A substrate in any direction can be used as long as the symmetry and straightness of the quantum well are not affected. Of course, the same can be said for the off-angle direction. The V groove of the present invention is
It is provided on a substrate or an epitaxial layer grown on the substrate. The direction of the V groove is 10 ° from the <110> direction.
The following is preferable, and 5 ° or less is more preferable. 10
If it deviates from the <110> direction by more than °, the state of the side surface of the V groove is likely to be jagged and is not so preferable.

The active layer is provided at the bottom of the V groove. When the quantum well structure is used as the active layer, the thickness of the active layer is 20 nm for use as quantum wires.
The following is preferable, but it can be used up to about 50 nm. With respect to the composition and conductivity type of the active layer, any of those usually used can be used, and there is no particular limitation. When the strained active layer is locally grown as in the present invention, a stress applied to the strained active layer is smaller than that when the strained active layer is grown on a flat surface. Therefore, a thicker active layer is used. Is possible. In the present invention, since the active layer is provided on the bottom of the V-groove, it is possible to make a finer quantum wire.

In a preferred embodiment of the present invention, a clad layer epitaxially grown on the substrate is provided and V
A groove is provided to provide an active layer, and a second layer is formed on the active layer.
This is a structure in which a clad layer is provided. One of preferred structures of the present invention is that the inner and outer clad layers of the V-shaped structure which are in contact with each other at the slope of the V groove, the energy gap of the outer clad layer, and the energy gap of the inner clad layer. It has a larger relationship, and by adopting such a structure, the current can be concentrated in the active layer at the bottom of the V groove, so that it is particularly preferably used for a laser diode or the like.

The slope of the V groove is preferably the {111} B plane. The {111} B plane is III-V.
If it is a group compound semiconductor, only the group V has a surface {11
If the compound semiconductor is a II-VI group compound semiconductor, only the group VI becomes a {111} plane. This is due to the steric hindrance of group V atoms and V / III on the {111} B plane.
This is because the crystal growth is less likely to occur since> 1 and it is easy to start the growth from the bottom of the V groove. This phenomenon means that the stress from the {111} B plane is small when the strained active layer is grown, and the critical film thickness can be increased.

The V groove of the present invention is preferably formed by vapor phase etching. This is because when the V groove is formed by wet etching as in the conventional case, the bottom of the V groove tends to have a rounded shape, and when impurities remain on the etching surface or an oxide film is formed on the etching surface, This is because it is difficult to obtain a high quality active layer even if the active layer is provided in contact with each other.

Needless to say, the V-groove may have a structure having no length in the longitudinal direction, such as an inverted pyramid shape. As an example of a preferred method of manufacturing the structure of the present invention, first, a layer to be the first cladding layer is epitaxially grown on the substrate. The growth method used at this time is preferably a metal organic chemical vapor deposition method (MOCVD method). A stripe-shaped silicon nitride film is formed on the surface of the epitaxial wafer by using a patterning process such as a photolithography method. At this time, the stripe direction of the silicon nitride film is preferably the <110> direction. After that, by introducing an etching gas into the reactor for metal organic chemical vapor deposition (MOCVD) method, in-situ gas etching of the first cladding layer is performed using the silicon nitride film as a mask, and the tip is sharply pointed. Forming a V-groove,
The quantum wires and the second cladding layer are continuously grown in the V groove without exposing the substrate to the air as it is. At this time, HCl is a suitable etching gas.
Further, when this method is used, impurities are not left on the etching surface or an oxide film is not formed, so that a high-quality active layer can be obtained even if the active layer is directly grown on the etching surface. .

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the examples as long as the gist thereof is not exceeded. (Example 1) First, on a (100) GaAs substrate, M
GaAs layer (0.5 μm), Al _0.5 G by OCVD method
Then, a _0.5 As (2 μm) and a GaAs layer (20 nm) were formed in this order. A silicon nitride film is formed on the surface of this epitaxial substrate by the PCVD method, and a silicon nitride film with a width of 1 μm extending in the [011] direction is formed by the photolithography method.
Masks were formed in a shape of lining every 1 μm. The masked sample was set again in the MOCVD apparatus. After setting
In an arsine (AsH3) atmosphere, raise the temperature to 700 ° C,
Then, etching is performed using HCl gas, and {11
A V groove having 1} B faces on both side faces was formed. Immediately after the etching was stopped, while maintaining the temperature at 700 ° C., trimethylgallium (TMG) and trimethylindium (TMI) were supplied to form an In _0.2 Ga _0.8 As strained active layer in the V groove, and trimethylgallium (TMG) and trimethylindium were further formed together with TMG. Aluminum (TMA) is also supplied at the same time and 1 μm Al _0.5 G
a _0.5 As clad layer is formed, and arsine and TMG are used again.
Was supplied to form a 0.1 μm GaAs layer. An explanation of this manufacturing process is shown in FIG. At this time, {111}
Since it is difficult to grow epitaxially on the B surface, the growth does not occur on the sidewall of the V groove, and as a result, Ga is formed on the bottom of the V groove.
As quantum wires are formed in a self-aligned manner. Also, during the growth, by supplying HCl at about 1 sccm, which is about the same mole as the Group III source material, AlGa is deposited on the silicon nitride layer.
The precipitation of polycrystalline As was prevented. This method of supplying HCl during growth is suitable for use especially when the aluminum composition of the GaAlAs layer is 0.4 or more, and it enables selective growth of AlGaAs having a high aluminum composition, so that carriers for the active layer can be obtained. Is effective in confining

The sample thus grown was observed by SEM. This state is schematically shown in FIG. The under-etching phenomenon in which the etching spreads under the silicon nitride mask did not occur, and the V-groove had a sharp V-groove at the tip. Then, a fine wire of In _0.2 Ga _0.8 As was embedded only in the bottom portion of the V groove. When grown on a flat substrate, the integrated PL intensity sharply decreased when the strained quantum well thickness became 20 nm or more, whereas in the case of a thin wire, the integrated PL intensity up to 40 nm was obtained.
The strength did not decrease. These results indicate that not only a high-quality quantum wire with little damage could be easily obtained, but also the critical film thickness could be increased.

Example 2 A sample similar to that of Example 1 was prepared except that the composition of the buried cladding layer was changed to Al _0.3 Ga _0.7 As, and the PL emission intensity was examined at 77 K. As shown in FIG. A clear emission peak was observed from the In _0.2 Ga _0.8 As strained quantum wire (width 40 nm, height 20 nm), and an increase in emission intensity was observed in the sample of Example 1. This is because the carrier in the V groove is
Since there is an energy barrier on the side wall of the V-groove, it is considered that it is a result of being unable to go out of the V-groove and being concentrated on the active layer at the bottom of the V-groove. Such an effect is considered to be advantageous when manufacturing a laser device or the like.

[0017]

According to the present invention, a quantum wire having a high-quality strain can be easily obtained, and the efficiency of a semiconductor device can be improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing one mode created in Example 1 of the present invention.

FIG. 2 is an explanatory diagram of a manufacturing process used in Example 1 of the present invention.

FIG. 3 is a diagram showing a state of PL light emission at room temperature of the sample prepared in Example 1 of the present invention.

FIG. 4 is an explanatory diagram showing a typical example of a device using a conventional quantum wire.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideki Goto 1000, Higashihuinana-cho, Ushiku-shi, Ibaraki Mitsubishi Chemical Corporation Tsukuba Plant

Claims (5)

[Claims] 1. A semiconductor substrate or an epitaxial growth layer grown on a semiconductor substrate has a groove having a V-shaped cross section in at least a part thereof, and an active layer having a strain at the bottom of the V-shaped groove. A semiconductor device having a structure in which the active layer is provided and is filled with a clad layer. 2. The semiconductor device according to claim 1, wherein the active layer has a quantum well structure. 3. An inner and outer clad layer having a V-shaped structure in contact with the slope of the V-shaped groove, wherein the energy gap of the outer clad layer is greater than the energy gap of the inner clad layer. The semiconductor device according to claim 1, wherein the semiconductor device has an enlarged structure. 4. The semiconductor device according to claim 1, wherein the slope of the V-shaped groove is a {111} B plane. 5. The semiconductor device according to claim 1, wherein the V-shaped groove is formed by vapor phase etching.