JPH08125262A - Semiconductor light-emitting device having v-shaped groove structure - Google Patents

Abstract

PURPOSE: To provide a V-shaped groove structure, which can easily obtain a quantum fine wire of good quality. CONSTITUTION: A double heterostructure, wherein a first light guide layer of a refractive index larger than that of first and second clad layers is vertically inserted between the clad layers of the refractive index smaller than that of the guide layer, is epitaxially grown on a semiconductor substrate, a groove with a section formed into a V shape is provided in at least one part of an epitaxially grown layer of a double heterostructure and an active layer is provided on the bottom part of the groove with the section formed into the V shape. Moreover, the left and right parts of the active layer are brought into contact with the light guide layer and a third clad layer of a refractive index smaller than that of the active layer is provided on the upper part of the active layer. Thereby, a semiconductor device having a structure, wherein the active layer is buried in the V-shaped groove, is manufactured.

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, preferably a semiconductor light emitting 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.

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]

However, since the quantum wire is in a very small area, even if it is applied to a laser structure, the light density at the emitting surface tends to be very high, and the light output is very weak. There is a problem that you cannot get it. In addition to the characteristics, the following problems exist in terms of fabrication. 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, not only the establishment of a technique for producing high-quality quantum wires, but also the optimization of the structure around the quantum wires capable of sufficiently exhibiting the device characteristics is a current subject.

[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 of the present invention is to provide a first optical guide layer having a larger refractive index with first and second clad layers having a smaller refractive index. The double hetero structure sandwiched between the upper and lower sides is epitaxially grown on a semiconductor substrate, and a groove having a V-shaped cross section is formed in at least a part of the epitaxial growth layer of the double hetero structure. The active layer is provided, and the left and right sides of the active layer are in contact with the light guide layer, and the third cladding layer having a smaller refractive index than the active layer is provided on the active layer, whereby the active layer is formed. A semiconductor device having a structure embedded in a V groove, more preferably a second device having a refractive index smaller than that of the active layer and larger than that of the third cladding layer between the active layer and the third cladding layer.
A semiconductor device having a structure in which an optical guide layer is provided, the first cladding layer and the first optical guide layer are of the same first conductivity type, and the third cladding layer and the second optical guide layer are the same. Second
A semiconductor device having a second conductivity type or a high resistance, the active layer having a quantum well structure, and the slope of the V-shaped groove is {1
The semiconductor device having the 11} B plane and the V-shaped groove are easily achieved by the semiconductor device and the like formed by vapor phase etching.

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 some quantum effect can be obtained 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. In the present invention, a double hetero structure in which a first optical guide layer having a higher refractive index is vertically sandwiched by first and second cladding layers having a lower refractive index is epitaxially grown on a semiconductor substrate, and the double hetero structure is epitaxially grown. At least a part of the layer has a groove having a V-shaped cross section, an active layer is provided at the bottom of the V-shaped groove, and the left and right sides of the active layer are in contact with the light guide layer, By providing a third cladding layer having a smaller refractive index than the active layer on the active layer, a semiconductor device having a structure in which the active layer is embedded in the V groove, and the active layer is provided at the bottom of the V groove. Therefore, it is possible to create a quantum wire having excellent light emission characteristics.

In a preferred embodiment of the present invention, a second optical guide layer having a refractive index smaller than that of the active layer and larger than that of the third cladding layer is provided between the active layer and the third cladding layer. It is a structure, and by taking such a structure,
The laser light generated by the recombination of electrons and holes in the active layer made of quantum wires can be exuded around the quantum wires, and the light output can be increased. At this time, the first
When the refractive indices of the second light guide layer are the same, it is easy to obtain a circular beam with good symmetry. One of preferred structures of the present invention is that the first cladding layer and the first light guide layer are of the same first conductivity type, and the third cladding layer and the second light guide layer are the same. The second conductivity type, the second
The clad layer is of the second conductivity type or of high resistance, and by adopting such a structure, the current can be concentrated in the active layer at the bottom of the V groove, which is particularly suitable for a laser diode or the like. Used.

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 because crystal growth generally does not easily occur on the {111} B plane, and it is easy to start growth from the bottom of the V groove.

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. . Further, it goes without saying that a contact layer may be formed on the outermost surface of the growth layer in the V groove, if necessary.

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. (Embodiment 1) First, an n-type GaAs buffer layer (0.
5 μm), n-type Al _0.5 Ga _0.5 As clad layer (2 μm
m), n-type Al _0.2 Ga _0.8 As optical guide layer ( _0.5 μm)
m), undoped Al _0.5 Ga _0.5 As high resistance layer (1 μm
m) and an undoped GaAs cap layer (0.2 nm) were formed in this order. A silicon nitride film was formed on the surface of this epitaxial substrate by the PCVD method, and a silicon nitride film having a width of 1 μm extending in the [011] direction was masked by photolithography so as to be arranged at intervals of 1 μm. The masked sample was set again in the MOCVD apparatus. After setting, the temperature is raised to 700 ° C. in an arsine (AsH ₃ ) atmosphere, and then etching is performed using HCl gas.
V-grooves having {111} B planes on both side surfaces were formed. Immediately after stopping the etching, while maintaining the temperature at 700 ° C., trimethylgallium (TMG) was supplied to form a GaAs active layer of 3 nm in the V groove, and trimethylaluminum (TMA) was also supplied together with TMG.
0.3 μm p-type Al _0.8 Ga _0.2 As optical guide layer, 1 μm
m p-type Al _0.5 Ga _0.5 As clad layer was prepared, arsine and TMG were supplied again, and 0.1 μm p-type GaAs
A layer was formed. An explanation of this manufacturing process is shown in FIG.
At this time, since epitaxial growth is difficult on the {111} B plane, growth does not occur on the side wall of the V groove, and as a result, a GaAs quantum wire is formed in the bottom of the V groove in a self-aligned manner. Also, during the growth, HCl was supplied at about 1 sccm, which is about the same mole as the group III raw material, to prevent the deposition of AlGaAs polycrystals on the silicon nitride layer. The method of supplying HCl during this growth is
AlGaAs preferably used when the aluminum composition of the layer is 0.4 or more and having a high aluminum composition
Since it is possible to selectively grow the carrier, it is effective in confining carriers in the active layer.

Electrodes were formed on the upper and lower sides of the sample thus grown and cleaved into laser chips to produce laser devices. As shown in FIG. 1, laser oscillation was performed at a low threshold value of 1 mA, and an optical output of up to 5 mW was obtained. These results show that a quantum wire laser with high quality and practical use could be manufactured.

[0016]

According to the present invention, it becomes possible to easily manufacture a quantum wire laser capable of producing an optical output of high quality and capable of withstanding practical use.

[Brief description of drawings]

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

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

FIG. 3 is a diagram showing current-voltage characteristics of laser devices prepared in Examples 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 (6)

[Claims] 1. A double hetero structure in which a first optical guide layer having a larger refractive index is vertically sandwiched by first and second clad layers having a smaller refractive index, is epitaxially grown on a semiconductor substrate, and the double hetero structure is epitaxially grown. At least a part of the layer has a groove having a V-shaped cross section, an active layer is provided at the bottom of the V-shaped groove, and the left and right sides of the active layer are in contact with the light guide layer, A semiconductor device having a structure in which a third clad layer having a refractive index smaller than that of the active layer is provided on the active layer so that the active layer is embedded in a V groove. 2. A structure in which a second optical guide layer having a refractive index smaller than that of the active layer and larger than that of the third cladding layer is provided between the active layer and the third cladding layer. 1. The semiconductor device according to 1. 3. The first cladding layer and the first light guide layer are of the same first conductivity type, and the third cladding layer and the second light guide layer are of the same second conductivity type. The second clad layer has a second conductivity type or high resistance.
13. The semiconductor device according to claim 1. 4. The semiconductor device according to claim 1, wherein the active layer has a quantum well structure. 5. The semiconductor device according to claim 1, wherein the slope of the V-shaped groove is a {111} B plane. 6. The semiconductor device according to claim 1, wherein the V-shaped groove is formed by vapor phase etching.