JPH0562896A - Manufacture of semiconductor quantum box - Google Patents

Abstract

PURPOSE:To easily manufacture a semiconductor quantum box which gives adequate quantum effect by growing crystals in one with a larger band gap of two types of semiconductors, insularly growing the other with a smaller band gap thereon, and growing crystals in the one with a larger band gap thereon. CONSTITUTION:Two types of semiconductors with different band gaps and lattice constants are prepared. Crystals are grown in one type of semiconductor with a larger band gap (e.g. GaAs0.5P0.5), which forms the first semiconductor barrier crystal layer 18. Then, the other type with a smaller band gap (e.g. GaAs) is insularly and three-dimensionally grown as semiconductor box crystals 20 on the first semiconductor barrier crystal layer 18. Finally, the one with a larger band gap is placed on the first layer 18 with the semiconductor box crystals 20 insularly formed on it, and crystals are grown again, forming the second semiconductor barrier crystal layer 22 so that the box crystals 20 are buried in the second layer 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device utilizing a quantum effect, and more particularly to a method of manufacturing a semiconductor quantum box.

[0002]

2. Description of the Related Art As an element to which the quantum effect of semiconductor is applied, there is a semiconductor laser using a quantum well structure. Such a quantum well laser has characteristics such as higher emission efficiency and a narrower spectral line width than ordinary semiconductor lasers, while having an advantage that the emission wavelength can be controlled by the well width.

[0003]

By the way, the above-mentioned quantum well has conventionally been a semiconductor crystal that is small, that is, thin, to the extent that the quantum effect appears one-dimensionally. In order to be two-dimensional (quantum wire), 3
It is desirable to reduce the crystal dimensionally (quantum box),
As a result, the control range of the emission wavelength can be expanded. However, in order to form them by crystal growth, the crystal usually grows in a plane. Therefore, in the case of a quantum well, the growth time may be shortened. Coating the entire top surface of the and removing the coating in small portions to perform selective growth,
Alternatively, most of the crystals grown in a plane are removed by etching or the like. These methods, of course, involve complicated steps, but it is extremely difficult to form crystal grains to the extent that the quantum effect can be obtained, that is, crystals with a direction of 10 nm or less, and the expected results have not been obtained yet. It has not been obtained.

The present invention has been made in view of the above circumstances, and an object of the present invention is to easily manufacture a semiconductor quantum box capable of obtaining a sufficient quantum effect.

[0005]

To achieve the above object, the present invention provides a semiconductor box crystal having a size small enough to exhibit a quantum effect by a semiconductor barrier crystal having a band gap larger than that of the semiconductor box crystal. A method of manufacturing a semiconductor quantum box dimensionally enclosing, wherein (a) one of two types of semiconductors having different band gaps and lattice constants having a larger band gap is crystal-grown to form a first semiconductor barrier crystal layer. And (b) a step of three-dimensionally growing the semiconductor box crystal having the smaller band gap among the two types of semiconductors in an island shape on the first semiconductor barrier crystal layer, (c) Of the two types of semiconductors, the band gap is large so that the semiconductor box crystal is buried on the first semiconductor barrier crystal layer in which the semiconductor box crystal is formed in an island shape. It was again grown, characterized in that it comprises a step of forming a second semiconductor barrier crystal layer.

[0006]

That is, when a semiconductor having different lattice constants is grown on a substrate or an underlayer such as an epitaxial layer, the semiconductor crystals grow three-dimensionally in a large number of islands due to lattice mismatch at the initial stage. It is known that two-dimensional crystal growth occurs after the islands become large and continuous with each other, and the present invention utilizes such a phenomenon to form a semiconductor box crystal. Specifically, two kinds of semiconductors having both a band gap difference which can expect a quantum effect and a lattice constant difference which can expect a three-dimensional growth are used, and first, a semiconductor having a larger band gap is crystal-grown. When the first semiconductor barrier crystal layer is formed and then the semiconductor having the smaller bandgap is crystal-grown on the first semiconductor barrier crystal layer for a short time, the semiconductor becomes three-dimensional in an island shape due to the difference in lattice constant. By growth, a semiconductor box crystal with one side of about 10 nm or less is formed. Then, on the first semiconductor barrier crystal layer in which the semiconductor box crystal is formed in an island shape, the semiconductor having the larger band gap is crystal-grown again so that the semiconductor box crystal is buried, and the second semiconductor barrier crystal is grown. By forming the layer, a semiconductor quantum box in which a semiconductor box crystal having a size small enough to exhibit a quantum effect is three-dimensionally wrapped with a semiconductor barrier crystal having a band gap larger than that of the semiconductor box crystal is manufactured.

Thus, according to the manufacturing method of the present invention,
A semiconductor quantum box small enough to obtain a sufficient quantum effect can be easily manufactured only by growing crystals of two kinds of semiconductors.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a view for explaining the cross-sectional structure of an epitaxial wafer 10 having a semiconductor quantum box according to an embodiment of the present invention. On an n-GaP substrate 12 having a plane orientation (100), GaP buffer layer 14, GaAs _0.5 P
_0.5 / GaP strained superlattice layer 16, GaAs _0.5 P _0.5 1st
Semiconductor barrier crystal layer 18, GaAs semiconductor box crystal 20, G
The aAs _0.5 P _0.5 second semiconductor barrier crystal layer 22 is sequentially stacked. These semiconductors are epitaxially grown at atmospheric pressure using a vertical MOCVD (metal organic chemical vapor deposition) apparatus, and the thickness of the buffer layer 14 is about 0.5 μm.
The strained superlattice layer 16 is formed by alternately stacking GaAs _0.5 P _0.5 and GaP each having a thickness of about 10 nm for 10 cycles, and the first semiconductor barrier crystal layer 18 has a thickness of about 1.0 μm. is there. Further, the semiconductor box crystal 20 is
For example, a GaAs semiconductor is crystal-grown on the first semiconductor barrier crystal layer 18 only for a time for crystal growth of about 5 nm in terms of two-dimensional growth.

Here, the band gap Eg and the lattice constant of GaAs _0.5 P _0.5 forming the first semiconductor barrier crystal layer 18 are 1.83 eV and 0.5552 nm, respectively, and the band gap of GaAs forming the semiconductor box crystal 20. Eg and lattice constant are 1.42 eV, 0.
It is 5653 nm. Since the lattice constants are different as described above, GaAs, which is crystal-grown on the first semiconductor barrier crystal layer 18 for a short time, is three-dimensionally grown in a large number of islands due to the lattice mismatch and becomes the semiconductor box crystal 20. . When this semiconductor box crystal 20 was photographed with a transmission electron microscope, it was in the shape of a quadrangular pyramid with one side of about 10 nm.
This is the size at which the quantum effect can be fully expected. Then, the semiconductor box crystal 2 having a large number of quadrangular pyramid shapes in this way
The second semiconductor barrier crystal layer 22 having a thickness of about 0.5 μm was formed on the first semiconductor barrier crystal layer 18 in which 0 was formed. Since the second semiconductor barrier crystal layer 22 is made of GaAs _0.5 P _0.5, which is the same as the first semiconductor barrier crystal layer 18, the GaAs semiconductor box crystal 20 is three-dimensionally enclosed by GaAs _0.5 P _0.5 having a large band gap. , A semiconductor quantum box is formed. In this example, GaA
s _0.5 P _0.5 and GaAs correspond to two types of semiconductors having different band gaps and lattice constants. The film thickness of each semiconductor in FIG. 1 is not necessarily shown in an accurate ratio.

Then, in order to confirm the quantum effect of the thus-fabricated epitaxial wafer 10, a photoluminescence spectrum at room temperature was measured using an Ar ion laser having a wavelength of 514.5 nm as an excitation light source. The results are shown in Table 1 and FIG. 2 in comparison with a normal GaAs crystal (bulk).

[0012]

As is clear from the above results, in the epitaxial wafer 10 of the present embodiment, that is, the GaAs quantum box, the emission wavelength peak is largely shifted to the short wavelength side, the emission intensity is about 2.87 times, and the half width is 2 minutes. It is 1 or less, and it can be seen that a good quantum box is formed. In addition,
The emission wavelength can be controlled by changing the size of the semiconductor box crystal 20, that is, the crystal growth time.

As described above, according to the epitaxial wafer 10 of this embodiment, the expected quantum effect can be obtained, and the epitaxial wafer 10 has a MOC.
It can be easily manufactured using a VD device.

Next, another embodiment of the present invention will be described.

FIG. 3 is a view for explaining the cross-sectional structure of a light emitting diode 30 manufactured according to the method of the present invention. An n-GaP buffer layer 34 and GaAs _0.5 are formed on an n-GaP substrate 32 having a plane orientation of (100). P _0.5 / GaP strained superlattice layer 36, n-GaAs _0.5 P _0.5 clad layer 38, active layer 40, p-GaAs _0.5 P _0.5 clad layer 42, p ⁺ −
The GaAs cap layer 44 is sequentially stacked, and the active layer 40 includes an undoped GaAs _0.5 P _0.5 first semiconductor barrier crystal layer 46, a GaAs semiconductor box crystal 48, and an undoped G layer.
aAs _0.5 P _0.5 It is composed of the second semiconductor barrier crystal layer 50. In addition, the lower surface of the substrate 32 and the cap layer 44
Electrodes 52 and 54 are provided on the upper surface of each.

The light emitting diode 30 is also one in which each semiconductor crystal is sequentially epitaxially grown on the substrate 32 by using the MOCVD apparatus as in the first embodiment, and the thickness of the buffer layer 34 is about 0.5 μm. , Strained superlattice layer 3
6 is about 10 for GaAs _0.5 P _0.5 and GaP, respectively.
It is a laminate of 10 cycles alternately with a thickness of nm,
The clad layer 38 has a thickness of about 4 μm, and the first semiconductor barrier crystal layer 46 has a thickness of about 0.1 μm. The semiconductor box crystal 48 is about 5 in terms of two-dimensional growth as in the above-mentioned embodiment.
nm, a GaAs semiconductor is crystal-grown on the first semiconductor barrier crystal layer 46 for the time for crystal growth, and is formed in a large number of islands due to lattice mismatch, and the second semiconductor barrier crystal layer 50 is formed thereon. Was formed to a thickness of about 0.1 μm. As a result, GaA having a relatively small band gap
s semiconductor box crystal 48 has a large band gap of Ga
As _0.5 P _0.5 first semiconductor barrier crystal layer 46 and second
A semiconductor quantum box that is three-dimensionally wrapped by the semiconductor barrier crystal layer 50 is formed. The thickness of the clad layer 42 formed on the second semiconductor barrier crystal layer 50 is about 4
μm, and the thickness of the cap layer 44 is about 0.2 μm. The film thickness of each semiconductor in FIG. 3 is not necessarily shown in an accurate ratio.

Then, the light emitting diode 30 manufactured in this manner and the undoped G having an active layer of about 0.2 μm are formed.
The light output was measured using a light emitting diode having a normal double hetero structure made of aAs _0.38 P _0.62, and the results shown in FIG. 4 were obtained. In FIG. 4, Q
The graph indicated by B-LED relates to the light emitting diode 30 of this embodiment, and the graph indicated by DH-LED relates to the light emitting diode of the double hetero structure. According to this, it can be seen that a light output of about 2.7 times can be obtained. That is, a good quantum box is formed also in this embodiment.

Although the embodiments of the present invention have been described in detail with reference to the drawings, the present invention can be implemented in other modes.

For example, in the above embodiment, GaAs _0.5 P
_{Although the} case where the semiconductor quantum box is formed of _0.5 and GaAs has been described, the difference in lattice constant from GaAs can be changed by changing the composition ratio of As and P of GaAs _0.5 P _0.5 . Of course, it is possible to form the quantum box by using other semiconductors having different band gaps and lattice constants.

Although the GaAsP light emitting diode 30 has been described in the second embodiment, AlGaAs or I
The present invention can also be applied to the production of other light emitting diodes such as nP or other semiconductor elements such as semiconductor lasers.

Although both the first semiconductor barrier crystal layer 46 and the second semiconductor barrier crystal layer 50 of the second embodiment are undoped GaAs _0.5 P _0.5 , one is p type and the other is n type. As a result, a quantum box can be formed at the interface of the pn junction.

In the above embodiment, the semiconductor box crystal 20,
Although only 48 is provided as a single layer, multiple semiconductor box crystals can be provided with the semiconductor barrier crystal layer sandwiched therebetween.

Although the semiconductor box crystal has a quadrangular pyramid shape in the above embodiment, it may be formed in other shapes such as a quadrangular pyramid and a rectangular parallelepiped.

In the above embodiment, the case where the semiconductor is crystal-grown by using the MOCVD apparatus has been described.
Other crystal growth methods such as molecular beam epitaxy can also be employed.

Although not illustrated one by one, the present invention can be implemented in various modified and improved modes based on the knowledge of those skilled in the art.

[Brief description of drawings]

FIG. 1 is a structural diagram illustrating an example of an epitaxial wafer manufactured according to the method of the present invention.

2 is an epitaxial wafer of FIG. 1 and a normal Ga
It is a figure which shows the light emission wavelength characteristic of As crystal.

FIG. 3 is a structural diagram illustrating an example of a light emitting diode manufactured according to the method of the present invention.

FIG. 4 is a diagram showing the light output of the light emitting diode of FIG. 3 and a conventional double heterostructure light emitting diode.

[Explanation of symbols]

 18: 1st semiconductor barrier crystal layer 20: Semiconductor box crystal 22: 2nd semiconductor barrier crystal layer 46: 1st semiconductor barrier crystal layer 48: Semiconductor box crystal 50: 2nd semiconductor barrier crystal layer

Claims (1)

[Claims] 1. A method of manufacturing a semiconductor quantum box, which comprises a semiconductor box crystal having a size small enough to exhibit a quantum effect and three-dimensionally wrapped by a semiconductor barrier crystal having a band gap larger than that of the semiconductor box crystal. Forming a first semiconductor barrier crystal layer by crystal growth of one of two kinds of semiconductors having different gaps and lattice constants, which has a larger band gap; and forming a first semiconductor barrier crystal layer on the first semiconductor barrier crystal layer. A step of three-dimensionally growing the semiconductor box crystal having a smaller band gap as the semiconductor box crystal in an island shape; and the semiconductor box crystal on the first semiconductor barrier crystal layer in which the semiconductor box crystal is formed in an island shape. 2 to be buried
A method of manufacturing a semiconductor quantum box, comprising a step of recrystallizing one having a larger bandgap among semiconductors of different types to form a second semiconductor barrier crystal layer.