JPH1131862A - Method of manufacturing semiconductor solid-state quantum structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for easily manufacturing a semiconductor solid- state quantum structure, wherein homogeneity in size and composition is good while density is sufficient as well. SOLUTION: A plurality of regions (resist parts 11) which is, of ruggedness structure, larger than in-surface size of a solid-state quantum structure but smaller than 5 times the in-surface size are formed on a first semiconductor layer (GaAs substrate 10), while a second semiconductor layer (Inx Ga1-x As mixed crystal, etc.), of different lattice constant is laminated, so that a solid- state quantum structure (InAs semiconductor solid quantum structure 13) is manufactured self-alignedly on the plurality of regions (11).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for fabricating a semiconductor three-dimensional quantum structure used for an active layer of a low-threshold semiconductor laser.

[0002]

2. Description of the Related Art Conventionally, as a method for producing a high-quality semiconductor three-dimensional quantum structure, a method of laminating semiconductors having different lattice constants so as to form a fine island-like structure has been often used. For example, a method of growing a three-dimensional quantum structure by growing InGaAs having a lattice constant different from that of GaAs on a GaAs layer is disclosed in Applied Physics Letters, Vol. 63, No. 23, 1993, 3203-3205.
Page (Applied Physics Letters, volume 63, No.23, 199
3 pp.3203-3205) and D. Leonard et al.
et al.).

For example, in such a method, GaAs
If InGaAs is grown on the (100) plane of s by molecular beam epitaxy, a quantum dot structure having a diameter of about 30 nm can be formed at a high density of about 10 ¹⁰ cm ⁻² or more.

[0004]

However, the following problems exist in such a conventional method for fabricating a self-formed semiconductor three-dimensional quantum structure.

First, when fabricating a semiconductor three-dimensional quantum structure on a flat substrate, the size of the semiconductor three-dimensional quantum structure usually varies by about 10 to 20 percent. In the case of using a self-forming fabrication method, the variation has such a value regardless of the material of the semiconductor three-dimensional quantum structure, the growth conditions, the orientation of the formation surface, and the like. Therefore, as for the emission line width from the semiconductor three-dimensional quantum structure, the originally expected narrow line width cannot be realized, and the emission line width becomes wider than that of an ordinary bulk semiconductor.

Further, a portion where a semiconductor three-dimensional quantum structure is easily formed selectively is formed on the substrate by means of etching or the like,
There is a technique for selectively forming a semiconductor three-dimensional quantum structure there. However, in this method, since one pattern in which the semiconductor three-dimensional quantum structure is formed has a wide area of about ten times the size of the semiconductor three-dimensional quantum structure, the density of the semiconductor three-dimensional quantum structure decreases, and as a result, It is also difficult to obtain a high emission intensity.

For the above reasons, in the prior art, the self-assembled three-dimensional semiconductor quantum structure has such a uniformity that the emission is smaller than the emission line width from the ordinary bulk semiconductor or quantum well structure. It is difficult to fabricate it.

An object of the present invention is to solve the problems of the prior art and to provide a method for easily producing a semiconductor three-dimensional quantum structure having good uniformity in size and composition and sufficient density. .

[0009]

According to the present invention, a three-dimensional quantum structure is formed in a self-forming manner by laminating a second semiconductor layer having a different lattice constant on a first semiconductor layer on a certain principal plane orientation. In the manufacturing method, a region or a region having a plane orientation larger than the in-plane size of the three-dimensional quantum structure and not more than 5 times the in-plane size, and having a plane orientation different from the principal plane orientation between the regions. Divided by non-indexed surfaces,
Forming a plurality of regions having the same plane orientation as the principal plane direction on the surface of the first semiconductor layer, and forming a three-dimensional quantum structure in a self-forming manner on the plurality of regions; This is a method for manufacturing a structure.

In the present invention, the semiconductor three-dimensional quantum structure is not manufactured on a flat substrate, but is formed on a surface uneven structure including a region of a specific size (specific area) divided by planes having different plane orientations. Are fabricated, and a semiconductor three-dimensional quantum structure is fabricated on each of the plurality of regions. Therefore, the atoms constituting the second semiconductor supplied on the planes having different plane orientations cannot move to the region, and are extremely affected only by the atoms constituting the second semiconductor supplied on the region. A large number of semiconductor three-dimensional quantum structures having a uniform size can be manufactured. In addition, since this region is appropriately small, there is no problem in terms of the density and the emission intensity of the semiconductor three-dimensional quantum structure. In particular, if a large number of regions have the same area, the total amount of atoms used for forming the structure also becomes the same in proportion to the area of each region, so that a large number of semiconductors with high uniformity in shape, size and composition A three-dimensional quantum structure can be manufactured.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below.

In the present invention, the size of the region on the first semiconductor layer for forming the three-dimensional quantum structure is larger than the in-plane size of the three-dimensional quantum structure and not more than five times the in-plane size (area ratio). What is necessary is just to determine suitably within a range. In particular, it is preferable to set the in-plane size of the three-dimensional quantum structure to twice to five times (area ratio). In order to manufacture many identical three-dimensional quantum structures, many regions having the same area may be formed.

The shape of this region is not particularly limited, and may be, for example, a circle as in Example 1 described later, or a polygon having the same side length as in Example 2 described later. (Such as a square). In the case of this polygon (such as a quadrangle), the area of the polygon is divided by a plane perpendicular to the principal plane direction, and the areas of the plurality of polygons are alternately formed in a positional relationship forming an uneven shape. it can.

The plane orientation of this region is not particularly limited as long as it is the same as the main plane orientation (growth main plane) on which the first semiconductor layer is formed. However, it is preferable that the (100) plane is usually used when a semiconductor three-dimensional quantum structure is produced in a self-forming manner. The plane orientation of this area is (100)
In the case of a plane, conditions for crystal growth of a semiconductor three-dimensional quantum structure are generally wide.

The plane separating the plurality of regions is a plane having a plane orientation different from the principal plane orientation (growth principal plane) or a plane having no plane orientation index. For example, Example 1 described later
Or a surface perpendicular to the principal plane orientation, for example, as in Example 2 described later.

In the present invention, the first semiconductor and the second semiconductor are not particularly limited, and various semiconductors which can be conventionally used for producing a three-dimensional quantum structure in a self-forming manner are used. it can. In particular, the first semiconductor is preferably GaAs or a Group III semiconductor mixed crystal lattice-matched to GaAs, InP or a Group III semiconductor mixed crystal lattice-matched to InP, and the second semiconductor is In _x Ga
_1-x As mixed crystal (In composition ratio x is more than 0 and 1 or less),
In _x Ga _1-x As mixed crystal (In composition ratio x is larger than 0.53 and 1 or less), InAs _x P _1-x mixed crystal (As composition ratio x is 0
Greater than 1).

Here, the first semiconductor is GaAs or G
In the case of a group III semiconductor mixed crystal lattice-matched to aAs,
In terms of realizing a good semiconductor quantum structure, the second semiconductor is
In _xGa_1-xAs mixed crystal (In composition ratio x is greater than 0 and 1
The following is preferred. The first semiconductor is I
Group III semiconductor mixed crystal lattice-matched to nP or InP
The second semiconductor is InAs_xP_1-xMixed crystal (As composition
The ratio x is preferably larger than 0 and equal to or smaller than 1).

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings.

Embodiment 1 FIG. 1 is a process chart of a method for fabricating a semiconductor three-dimensional quantum structure according to Embodiment 1.

First, as shown in FIG.
On the (100) surface of the substrate 10, the resist 11 is applied only to a large number of circular regions having a diameter of about 50 nm by electron beam exposure.
Exposure was performed so as to remain. Here, the pitch of the circular area is 1
00 nm. Subsequently, using this resist 11 as a mask, as shown in FIG.
Etching was performed to a thickness of about nm. Here, the etched region is a curved surface having no specific plane orientation index. After removing the resist, as shown in FIG. 1C, InAs12 is grown to a thickness of about 0.5 nm on the surface of the substrate by molecular beam epitaxy to form a large number of in-plane sizes (diameters) of about 20 nm. Semiconductor three-dimensional quantum structure (In
As quantum dots) 13 were produced in a self-forming manner.

As described above, when InAs is grown on flat (100) GaAs, it is known that a semiconductor three-dimensional quantum structure having a growth thickness of about 0.5 nm and a diameter of about 20 nm grows in a self-forming manner. . In this example, one InAs semiconductor three-dimensional quantum structure was formed on each of the flat regions having a diameter of 50 nm which were left unetched. This is because it is difficult for atoms attached to the surface other than the flat portion to move across the step. Further, as for InAs attached to the non-flat portion, the amount of InAs supplied to the surface region does not exceed the critical film thickness for forming the semiconductor three-dimensional quantum structure, so that the semiconductor three-dimensional quantum structure is not formed.

Here, in the semiconductor three-dimensional quantum structure formed one by one in each flat portion, atoms serving as raw materials for forming one structure are not only atoms supplied to each flat region, and this amount is It was almost constant because it was proportional to the area of each region. Therefore, the semiconductor three-dimensional quantum structure is formed from the same amount of atoms by precisely equalizing the area of each part, and the size is very uniform.

FIG. 2 is a graph showing an in-plane size distribution of the InAs three-dimensional quantum structure according to the present embodiment. As shown in this graph, the size distribution width is about 2%,
It was very small.

<Embodiment 2> FIG. 3 is a process chart of a method for manufacturing a semiconductor three-dimensional quantum structure of Embodiment 2.

First, as shown in FIG.
On the (100) surface of the substrate 10, a checkerboard pattern of 50 nm on a side was formed on the resist 11 by electron beam exposure. Then, using this pattern as a mask, FIG.
As shown in (b), a step of about 5 nm was formed between the convex portion and the concave portion by dry etching. This step does not have a specific plane orientation index. After removing the oxide film on the surface of the substrate by molecular beam epitaxy using this substrate, as shown in FIG. 3C, InAs 12 is grown on the surface to a thickness of about 0.5 nm, and a large number of The semiconductor three-dimensional quantum structure (InAs quantum dot) 13 was self-formed.

In this embodiment, one semiconductor three-dimensional quantum structure is formed in each of the projections and depressions. Also here, atoms as raw materials for forming one semiconductor three-dimensional quantum structure are constant in each region, so that a very uniform semiconductor three-dimensional quantum structure was realized.

<Embodiment 3> In Embodiments 1 and 2, Ga
Except that the semiconductor grown on As was changed to In _0.5 Ga _0.5 As, a similar process was performed, and the same favorable effect was obtained. In such a semiconductor three-dimensional quantum structure using a mixed crystal material, it is necessary to control the composition distribution between the structures. According to this embodiment, however, one semiconductor three-dimensional quantum structure is formed from the same amount of atoms. Fabricated, and In, Ga
In both cases, the supply amounts to the respective regions were almost the same, so that a structure having a uniform composition was realized. Further, when the photoluminescence spectrum at room temperature of the structure in which the structure according to the present embodiment was embedded with GaAs was measured using an argon laser as an excitation source, the composition and size were made uniform, and a very good half-width of about 15 meV was obtained. The value was obtained.

Example 4 A similar process was performed as in Example 2, except that InP was used as the substrate.
Here, a (100) plane was used as a surface, and a plane perpendicular to the (100) plane was formed between the flat portions composed of the (100) plane by a reactive dry etching technique. On this surface, gas source molecular beam epitaxy
As was grown to 0.4 nm. Then, as in Example 2, a three-dimensional quantum structure made of InAs was formed on each flat portion. This structure is the same as that shown in FIG. 3C used in the description of the second embodiment, and the variation in the in-plane size of the semiconductor three-dimensional quantum structure was as good as about 2%.

In the first to fourth embodiments, the GaAs substrate,
Alternatively, the process of forming a pattern on an InP substrate and self-forming a three-dimensional quantum structure of a strained semiconductor thereon has been described, but the material system used in the present invention is limited to those on these substrates. Not the other II
An IV group semiconductor, a II VI group semiconductor, or the like may be used.

The pattern forming method is not limited to the method using the electron beam exposure technique and the dry etching technique, but may use other exposure techniques and etching techniques.
Alternatively, a unique surface structure on the semiconductor surface that appears during crystal growth may be used.

[0031]

As described above, according to the manufacturing method of the present invention, it is possible to easily produce a semiconductor three-dimensional quantum structure having a very small size and composition distribution, good uniformity thereof, and sufficient density. Can be made. In particular, when the uniformity of the size and composition of the semiconductor three-dimensional quantum structure is improved by the present invention, the emission line width and the like can be ultimately reduced.
The semiconductor three-dimensional quantum structure manufactured according to the present invention is extremely useful as an active layer of a semiconductor laser having ideal characteristics (an active layer of a semiconductor laser with a low threshold utilizing a narrow emission width).

[Brief description of the drawings]

FIG. 1 is a process chart of Example 1 of the present invention.

FIG. 2 is a graph showing an in-plane size distribution of a semiconductor three-dimensional quantum structure manufactured in Example 1.

FIG. 3 is a process chart of Example 2 of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 GaAs (100) substrate 11 Resist 12 InAs 13 Semiconductor three-dimensional quantum structure by InAs

Claims (8)

[Claims] 1. A method according to claim 1, wherein on a first semiconductor layer on a certain principal plane orientation,
In a method of self-forming a three-dimensional quantum structure by laminating second semiconductor layers having different lattice constants, a three-dimensional quantum structure having a size larger than the in-plane size of the three-dimensional quantum structure and not more than 5 times the in-plane size is provided. A plurality of regions having the same plane orientation as the main plane orientation, divided by a plane having a plane orientation different from the main plane orientation or a plane having no plane orientation index between the regions. A method for manufacturing a semiconductor three-dimensional quantum structure, comprising: forming a three-dimensional quantum structure on a surface of one semiconductor layer; 2. The method for manufacturing a semiconductor three-dimensional quantum structure according to claim 1, wherein the size of the region is at least two times and at most five times the in-plane size of the three-dimensional quantum structure. 3. The method for manufacturing a semiconductor three-dimensional quantum structure according to claim 1, wherein the shape of the region is a polygon having the same side length. 4. The polygonal region is divided by a plane perpendicular to the main surface direction, and the plurality of polygonal regions are in a positional relationship of alternately forming a concavo-convex shape.
A manufacturing method of the semiconductor three-dimensional quantum structure according to the above. 5. The method according to claim 1, wherein the principal plane direction is a (100) plane. 6. The method according to claim 1, wherein the first semiconductor is GaAs or GaAs.
6. A mixed crystal of group III semiconductors lattice-matched to the following, wherein the second semiconductor is an In _x Ga _{1 -x} As mixed crystal and an In composition ratio x is greater than 0 and 1 or less. 3. The method for producing a semiconductor three-dimensional quantum structure according to the above item. 7. The first semiconductor is InP or a Group III semiconductor mixed crystal lattice-matched to InP, and the second semiconductor is IP.
n In _x Ga _1-x As mixed crystal, a method for manufacturing a semiconductor steric quantum structure of any one of claims 1-5 In composition ratio x is less than 1 greater than 0.53. 8. The semiconductor according to claim 1, wherein the first semiconductor is InP or a Group III semiconductor mixed crystal lattice-matched to InP, and the second semiconductor is IP.
The method for producing a semiconductor three-dimensional quantum structure according to any one of claims 1 to 5, wherein the composition ratio x of As is greater than 0 and equal to or less than _{1 in the} nAs _x P _1-x mixed crystal.