A. P. Vasilenko

Dependence of plastic relaxation in GaAs films on nucleation of the first as monolayer on Si(001) substrates

The structure of GaAs films grown on Si(001) vicinal substrates (6° rotation about 〈011〉 axis) formed in two ways of nucleation, As deposition on Si and substitution of Si monolayer by As monolayer, is studied. X-ray diffractometry is used to find that the rotation direction of a crystal lattice depends on the manner of nucleation. An optional model of the formation of film dislocation structures is proposed.

Influence of the Misfit-Dislocation Screw Component on the Formation of Threading Dislocations in Semiconductor Heterostructures

In heterostructures with the (001) interface and diamond and sphalerite crystal lattices, the total relief of mismatch stresses by introducing two mutually perpendicular arrays of 60° misfit dislocations (MDs) was shown to be possible only if their screw components were of the same type. In the opposite case, it was necessary to introduce additional MD arrays that increased the probability of formation of threading dislocations in an epitaxial film. When the process is nonoptimal and two mutually perpendicular arrays are introduced with opposite types of screw components, excess energy of long-range shear stresses is accumulated. Examples of nonoptimal introduction of misfit dislocations are the operation of the Frank-Read and Hagen-Strunk modified dislocation sources. The relaxation process was simulated and investigated experimentally.

Optimal and Nonoptimal Misfit Stress Relaxation in a Semiconductor Heterosystem

Misfit stress relaxation processes in a semiconductor heterosystem are divided into optimal and nonoptimal. Depending on the type of a process and degree of its completeness, four variants of a uniform stress field are established and experimentally detected in the surface layer of an epitaxial film. The interaction between threading dislocations that favors the transformation of nonoptimal relaxation into optimal is investigated.

Strained germanium films in Ge/InGaAs/GaAs heterostructures: Formation of edge misfit dislocations at the Ge/InGaAs interface

Heterostructures of the “strained Ge film/artificial InGaAs layer/GaAs substrate” type have been grown by molecular beam epitaxy. A specific feature of these structures is that the plastically relaxed (buffer) InGaAs layer has the density of threading dislocations on a level of 105–106 cm−2. These dislocations penetrate into the strained Ge layer to become sources of both 60° and 90° (edge) misfit dislocations (MDs). Using the transmission electron microscopy, both MD types have been found at the Ge/InGaAs interface. It has been shown that the presence of threading dislocations inherited from the buffer layer in a tensile-strained Ge film favors the formation of edge dislocations at the Ge/InGaAs interface even in the case of small elastic deformations in the strained film. Possible mechanisms of the formation of edge MDs have been considered, including (i) accidental collision of complementary parallel 60° MDs propagating in the mirror-tilted {111} planes, (ii) induced nucleation of a second 60° MD and its interaction with the primary 60° MD, and (iii) interaction of two complementary MDs after a cross-slip of one of them. Calculations have demonstrated that a critical layer thickness (hc) for the appearance of edge MDs is considerably smaller than hc for 60° MDs.

Stress relaxation by generation of L-shape misfit dislocations in (001) heterostructures with diamond and sphalerite lattices

Abstract The problem of generation of L-shape misfit dislocations (MDs) is investigated for (001) heterosystems with diamond and sphalerite crystal structures. These 60° MDs can be formed by modified Frank–Read dislocation sources as well as by Hagen–Strunk ones. The analysis shows that perpendicular dislocation lines included in L-shape MDs have different types of screw dislocation components (namely, left-screw and right-screw ones). As a result, the stress-releasing process tends to slow preventing further generation of L-shape dislocations and annihilation of threading dislocations (TDs). To minimize density of TDs and to form equilibrium plane MD networks at the final stage of stresses relaxation process, it is necessary to generate mutually perpendicular MD arrays with the same types of screw dislocation components.

Crystal perfection of GaP films grown on Si substrates by solid-source MBE with atomic hydrogen

GaP films have been grown by migration-enhanced epitaxy on Si (001) substrates tilted by 6° about the 〈011〉 axis. High-energy electron diffraction, transmission electron microscopy, and X-ray diffraction analysis were used to demonstrate that introduction of atomic hydrogen in the course of epitaxy markedly improves the overall structural quality of GaP films. Up to thicknesses of about 0.1 μm, the full width at half-maximum of the (004) reflection in the X-ray diffraction pattern of these films almost coincides with the theoretical value for defect-free films, which indicates that their state is nearly pseudomorphic.

An X-ray epitaxial film interferometer as a tool for studying the structure of a semiconductor heterosystem

An X-ray epitaxial film interferometer is described that makes it possible to measure the deflections of the atomic planes of a film, which are parallel to the interface, with a sensitivity of several tenth of an angstrom. The size of the region under study in the interface plane ranges from several tens of microns to centimeters. As a result, a change in the angle of inclination of the reflecting atomic planes of 0.002″–2″ is recorded. A single-crystal Si substrate and a Si film grown using the molecular-beam epitaxy technique serve as the diffracting crystals of the X-ray interferometer. Porous silicon functions as a separating nondiffracting layer. The effect of earlier uncontrollable technological factors on the crystal lattice structure of a semiconductor heterostructure was detected.

Investigation of the atomic crystal plane relief by X-ray epitaxial film interferometer

Translation Moire pictures were first observed in double crystal X-ray topographs recorded for the epitaxial Si/Si porous layer/Si substrate heterosystem. The relief of atomic (hkl) planes, which are usually transformed into curved surfaces in real epitaxial films, can be studied using these pictures. Their relief amplitude is registered with accuracy better than 0.1 nm. Distorted crystal lattice areas vary from dozens micrometers to several millimeters along the directions parallel to the interface. The effect of technological factors non-registered before on the lattice distortions is observed. Absorbates are found to influence the thickness of a porous Si layer under ordinary conditions as well as in organic solvents (toluene and acetone).

X-Ray Diffraction Analysis of Epitaxial Layers with the Properties of a Dislocation Filter

An approach to instant testing of epitaxial films with a sharp decrease in the threading dislocation density is proposed. High-resolution X-ray diffractometry, including reciprocal space mapping, has been used. The structure of GaAs/Si(001) heterosystems with low-temperature GaAs layers has been analyzed. A decrease in the density of threading dislocations in the GaAs film with the formation of a small-angle boundary has been detected.

Analysis of the Stress Relieving Process in a Semiconductor Heterosystem with a (013) Interface

A theoretical analysis of the process of introducing misfit dislocations into a semiconductor heterostructure with a (013) interface is performed by assuming conditions of quasi-equilibrium process. The mechanism of generation is established for those misfit dislocations, which do not meet the requirement of minimum critical film thickness. The calculations are performed on the basis of the force balance model and allow for the shear stress field in the film and the type of the screw dislocation component.