JPH0529651A - Semiconductor device - Google Patents

Abstract

PURPOSE:To provide a direct-transition semiconductor, in which the probability of transition by light between the conduction band and valence band is increased, by a zone-folding of energy band. CONSTITUTION:A cubic crystal structure is provided in which its unit cell includes atomic silicon layers and atomic germanium layers stacked in the (111)-plane, and the silicon and germanium layers totals to an even number; a zone-folding of energy band is shown in the figure. In the figure are shown the gamma point in a wave-vector space 11, the L point 12, a conduction band 14, a valence band 15, and a conduction band 16 that contains silicon atoms only. In such a semiconductor, the L point is folded onto the gamma point, so it becomes a direct-transition semiconductor having the gamma point on the bottom of the conduction band. The L point in the wave-vector space, whose symmetry is owing more than 50% to the s-orbit, is folded onto the gamma point. Therefore, it is possible to increase the probability of transition by light between the conduction band and valence band.

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 zone folding of energy band.

[0002]

2. Description of the Related Art A conventional semiconductor device using zone folding of an energy band is composed of silicon and germanium atoms, and the sum of the total number of silicon and germanium atomic layers in a unit cell is even, and the crystal orientation is (100). FIG. 3 shows a state in which energy band zone folding is performed in a cubic system structure stacked in the plane direction. 1 is the gamma point in wave number space,
2 is an X point, and 3 is an X point when only silicon atoms are used. 4 is a conduction band, 5 is a valence band, and 6 is a conduction band in the case of only silicon atoms.

In the semiconductor device configured as described above, since the X point of 3 is folded back to the gamma point, the bottom of the conduction band becomes the gamma point and the semiconductor becomes a direct transition type semiconductor.

[0004]

However, in the above-mentioned structure, although the X point of 3 is folded back to the gamma point, the symmetry at the original X point 3 is 50% or more.
Since there is a contribution from the P orbital, there is a problem that the transition probability due to light between the conduction band valence bands at the gamma point becomes very small.

In view of the above points, an object of the present invention is to provide a semiconductor device which utilizes the zone folding of the energy band and has a large probability of light transition between conduction band valence bands at the gamma point.

[0006]

A cubic structure including at least a silicon atomic layer, wherein the sum of the total number of other atomic layers and the silicon atomic layer in the unit lattice is even, and stacked in the (111) plane direction of the crystal orientation. A semiconductor device having a crystal structure is formed.

[0007]

According to the present invention, due to the above-described structure, the L-point, which has a contribution from the S orbit with a symmetry of 50% or more in the wave number space, is folded back to the gamma point. Therefore, the transition probability is increased.

[0008]

FIG. 1 is an energy band diagram of a semiconductor device according to a first embodiment of the present invention, in which the sum of the total number of silicon and germanium atomic layers in the unit cell is even and the crystal orientation is in the (111) plane direction. This is a stacked cubic structure, showing how the energy band is zone-folded. 11 is a gamma point in the wave number space, 12 is an El point, and 13 is an El point in the case of only silicon atoms. 14 is a conduction band, 15 is a valence band, and 16 is a conduction band in the case of only silicon atoms.

In the semiconductor device configured as described above, since the 13 L-point is folded back to the gamma point, the bottom of the conduction band becomes the gamma point, and the semiconductor becomes a direct transition type, and is symmetric in the wave number space. Since the L-point, which has a contribution from the S orbit of more than 50%, is folded back to the gamma point, the transition probability due to light between the conduction band valence bands at the gamma point increases.

FIG. 2 is an energy band diagram of a semiconductor device according to a second embodiment of the present invention. The sum of the total number of aluminum, gallium and phosphorus atomic layers in the unit cell is even, and the crystal orientation is in the (111) plane direction. It shows a state in which the energy band is folded in a cubic system structure stacked in. 21 is a gamma point in the wave number space, 22 is an El point, and 23 is an El point in the case of only aluminum and phosphorus atoms. 24 is a conduction band, 25 is a valence band, and 26 is a conduction band in the case of only aluminum and phosphorus atoms.

In the semiconductor device configured as described above, since the L-point of 23 is folded back to the gamma point, the bottom of the conduction band becomes the gamma point, and the semiconductor becomes a direct transition type, and is symmetric in the wave number space. Since the L-point, which has a contribution from the S orbit of more than 50%, is folded back to the gamma point, the transition probability due to light between the conduction band valence bands at the gamma point increases.

[0012]

As described above, according to the present invention,
By carrying out energy band zone folding, it is possible to make the semiconductor a direct transition type and to increase the probability of transition due to light between conduction band valence bands at the gamma point, which has a large practical effect.

[Brief description of drawings]

FIG. 1 is an energy band diagram of a semiconductor device according to an embodiment of the present invention.

FIG. 2 is an energy band diagram of a semiconductor device according to another embodiment of the present invention.

FIG. 3 is an energy band diagram of a conventional semiconductor device.

[Explanation of symbols]

11, 21 gamma point 14, 24 conduction band 15, 25 valence band 16, 26 conduction band 12, 22 el points 13, 23 el point

Claims (3)

[Claims] 1. A cubic system structure including at least a germanium atomic layer, wherein the sum of the total number of other atomic layers and the germanium atomic layer in the unit cell is an even number, and stacked in the (111) plane direction of the crystal orientation. Semiconductor device. 2. A cubic system structure including at least a silicon atomic layer, wherein the sum of the total number of other atomic layers and the silicon atomic layer in the unit cell is an even number, and stacked in the (111) plane direction of the crystal orientation. Semiconductor device. 3. Laminating in the (111) plane direction of the crystal orientation, which is composed of at least three kinds of group III and group V atomic layers and has an even sum of the total number of group III and group V atomic layers in the unit cell. Cubic structure semiconductor device.