JPS61102083A - Super-lattice structure - Google Patents

Abstract

PURPOSE:To obtain a super lattice structure having flatness on the junction interface in an atomic scale, by mating the hetero junction interface having a super lattice structure, which is formed by laminating different semiconductive material having zincblende system crystal lattices alternately, with the plane (110). CONSTITUTION:Super lattice structure is formed by laminating two kinds of layers of semiconductive material having zincblende system crystal lattice 1A-1D and 2A-2D alternately, then its hetero junction interface is mated with the plane (110). The plane (110) is coasely filled with atoms compared with the plane (100), with the result that impurity deeply penetrates into the inside of the crystal without being much obstructed by the atoms in the material, retaining the flatness of the hetero junction interface in spite of the dispersion of the impurity.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to superlattice structures.

(Prior Art) Semiconductor elements that utilize the Dojiwell effect or quasi-two-dimensional electron gas effect of electronic states in a semiconductor superlattice structure are being developed. For example, in semiconductor lasers, these devices have characteristics superior to conventional semiconductor lasers, such as superior light emission efficiency and high-temperature operating characteristics compared to normal double heterojunction semiconductor lasers, or new characteristics not previously available. It has a wide range of applications. The above superlattice structure (
It is obtained by epitaxially growing different semiconductor materials of several tens to hundreds of angstroms on a 100) plane alternately using a crystal growth method with a high degree of film thickness controllability, such as molecular beam epitaxy or organometallic pyrolysis. (Applied Fixtures Letters (A)
pPI, Phys.

Lett, Volume 39, 1981, Page 786).

(Problems with the Prior Art) However, the superlattice structure obtained using the (100) plane as a heterojunction surface has at least the following two drawbacks. The first drawback is that the degree of perfection of each atomic layer during crystal growth is insufficient, so there are irregularities on an atomic scale at the heterojunction interface, which causes quantum quasi This is the cause of the variation in ranking. Variations in quantum levels have undesirable effects on device characteristics, such as localization of spatial electron distribution and broadening of the emission spectrum. A second drawback is that the superlattice structure is destroyed by doping impurities. This occurs because the diffusion of impurity atoms in the crystal progresses while changing the arrangement of host atoms on lattice points.

Destruction of the superlattice structure is extremely undesirable because it eliminates the quantum well effect itself.

(Objective of the Invention) An object of the present invention is to eliminate the above-mentioned drawbacks and to provide a superlattice structure having flatness of the heterojunction interface on an atomic scale.

(Structure of the Invention) According to the present invention, the above object is achieved by making the heterojunction interface of the superlattice structure stacked in sequence coincide with the (110) plane of the zincblende crystal lattice. I can do it.

(Operation/Principle of the Invention) When the heterojunction interface is made into a (100) plane as in the past, as shown in the crystal cross section in Figure 3(a), the atoms in contact with the heterojunction interface are Only two of the bonds are bonded to atoms on the side of the semiconductor material to which they belong, and the number of bonds bonded to atoms on the side of the different semiconductor across the heterojunction interface is 92 bonds per atom. . New atoms are attached to fill these two bonds, and crystal growth progresses, but even if the surface is uneven during growth, the growth in the direction perpendicular to the surface is fast, so the unevenness on an atomic layer scale increases. An actual heterojunction interface is formed without being relaxed.

This ((on the other hand, as in the present invention, the heterojunction interface is (11
0) If Lfr is used, the situation will be improved. Up to three of them are bonded to atoms on the side of the semiconductor material to which they belong, and only one bond per atom is bonded to atoms on the side of a different semiconductor across the heterojunction interface. This difference causes a difference in the degree of completion for each atomic layer during crystal growth. In other words, in the case of growth on the (110) plane, if the surface has irregularities on an atomic layer scale during growth, crystal growth occurs more rapidly in the direction parallel to the plane than in the direction perpendicular to the plane, and the atoms It is easy to obtain a flat surface on a layer scale. More than(
The high stability of the 110) plane can also be understood from the fact that the normal opening plane of zinc blende crystals is the (110) plane.

Further, the superlattice structure with the (110) plane as the heterojunction interface has excellent stability against impurity diffusion.

The crystal lattice viewed from the direction perpendicular to the heterojunction interface appears to be exactly the same as those shown in FIG. 3 (a) and (b).

Atoms are densely packed on the (100) plane, and when impurities cross the heterojunction interface and diffuse through the crystal, they proceed while replacing host atoms on the lattice points. As a result, even if a flat heterojunction interface is obtained during crystal growth, the flatness of the heterojunction interface is lost due to impurity diffusion.

On the other hand, if the (110) plane is used as a heterojunction interface as in the present invention, the atoms are packed more loosely than on the (100) plane, so impurities are not hindered by the host atoms and can be absorbed inside the crystal. can penetrate deeply (channeling). An impurity atom can be located on a lattice point by replacing the host atom on the lattice point at most once. In the end, on the (110) plane (
It is understood that the heterojunction interface is less likely to collapse due to impurity diffusion than the 100) plane.

After all, if we try to obtain a quantum well effect or a quasi-two-dimensional electron gas effect in the electronic state using a superlattice structure, we can create a superlattice structure with the (110) plane of the crystal as the heterojunction interface as shown in Figure 1. It can be said that hiring is effective. In FIG. 1, IA ID indicates a region of one semiconductor material forming a superlattice structure, and 2 or 2D indicates a region of the other semiconductor material. An appropriate combination of two types of semiconductor materials to obtain a superlattice structure is GjLA3-AIAB, I, taking into account lattice matching at the heterojunction interface.
nAa-Garb, GaSb-AA! Sb,
Many systems such as GaAs-Zn5e are possible.

(Example) Examples using the advantageous characteristics of the present invention will be described below.

FIG. 2 is an example of a semiconductor laser according to the present invention having a GaAs-AlA3 superlattice structure with a (110) plane as a heterojunction interface as an active layer. n with (110) plane
A fourth cladding layer 4 made of n-type AlxGa-XAs and a second cladding layer 6 made of Se2-type AIXG & 1-xAS are epitaxially grown on a GaAs type substrate 3, and a second cladding layer 6 made of Se2 type AIXG & 1-xAS is grown by epitaxial growth. Electrodes 7 and 8 are provided for injecting a current. Naturally, the energy gap between the cladding layers 3 and 5 is also larger than that of the active layer 4 in order to produce laser operation. The reflecting surface for forming the laser resonator is (110) as shown in the figure.
Two parallel planes perpendicular to the plane, namely (110) and (
110) Just wrap around the surface. In this way, from an active layer with a superlattice structure in which the heterojunction interface has high integrity, the spectral width narrows, reflecting the singularity of the density of states of the quasi-two-dimensional electron gas confined in the quantum well of the superlattice structure. Moreover, highly efficient laser emission can be reliably obtained.

In this example, the simplest structure as a semiconductor laser is shown for explanation, but even if a complicated structure is adopted to improve the device operating characteristics of the semiconductor laser, for example, to introduce a light emission mode control mechanism, ( The situation remains the same as long as a superlattice structure is used in which the 110) plane is the heterojunction interface.

Further, although the above embodiments have been shown in connection with a semiconductor laser, a similar superlattice structure can be expected to exhibit excellent effects in semiconductor devices in which current flows parallel to the heterojunction interface. In other words, since the flatness of the heterojunction interface is extremely high, the probability of scattering of electrons moving along the interface is kept small, and high electron mobility can be expected.
This is advantageous for realizing ultra-high-speed operating semiconductor devices.

(Effects of the Invention) As explained above, by selecting the heterojunction interface of the superlattice structure to match the (110) plane of the zincblende crystal lattice, the atomic scale of the heterojunction interface can be improved. A superlattice structure that has excellent flatness and does not lose its flatness even when impurities are diffused can be obtained, and thereby a high-performance semiconductor laser having a narrow spectral width and high luminous efficiency can be realized.

Further, excellent devices such as semiconductor devices having high electron mobility can be realized.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a superlattice structure in the present invention, FIG. 2 is a diagram showing the structure of a semiconductor laser in an embodiment of the present invention,
FIG. 3 is a diagram showing a crystal structure for explaining the present invention in detail. In the figure, IA to ID...the first layer forming a superlattice structure.
2A to 2D... a layer made of a second semiconductor material forming a superlattice structure. 3... n-type semiconductor substrate having (110) plane, 4...
・N-type AlxGa1-xASAs cladding layer...Ga
Active layer of semiconductor laser using As-AIAS superlattice structure, 6... p-type AJxGa 1-, As cladding layer, 7... p1111! Pole, n-side electrode. -The beautiful patent attorney Susumu Uchihara ゛...144,\,-

Claims (1)

[Claims] A superlattice structure formed by alternately stacking different semiconductor materials having a zincblende crystal lattice, characterized in that the heterojunction interface is selected to coincide with the (110) plane of the crystal. .