Aleksei V. Kolesnikov

The dynamics of monoatomic steps on the Si(100) vicinal surface during molecular beam epitaxy (MBE) growth and annealing is studied based on the analysis of reflection high-energy electron diffraction intensity variations. During growth, the initially equally spaced A- and B-steps are getting closer: the width of the A-terraces decreases to a certain minimum value, which increases with increasing growth temperature. The number of Si monolayers deposited until the minimum distance between the A- and B steps is reached increases monotonically with increasing temperature. After interrupting the Si deposition flux (during annealing) the width of the A-terrace gradually increases to the initial value. The time of such relaxation to the initial configuration of the steps decreases with increasing temperature and increasing miscut angle. The observed behavior of the steps during annealing is in good agreement with the available theoretical models of the step dynamics and is explained by the presence of an exchange flux of Si atoms between the A- and B-steps due to the elastic interaction of the steps caused by the anisotropy of the elastic stress tensor on the reconstructed Si(100) surface. However, the available models fail to explain the experimentally observed monotonically increasing temperature dependence of the number of Si monolayers deposited until the steps approach each other during growth, which indicates the need to modify the model of incorporation of Si adatoms into steps in the case of high temperatures.

In this work, the convergence kinetics investigations of the S_A- and S_B-steps on Si(100) substrates with inclination 0.5^o and 0.1^o were carried out. Analysis of the time dependence of reflection high-energy electron diffraction (RHEED) intensity was used to establish the growth kinetics character on vicinal Si(100) surfaces. It is shown that, in a Si flow at the growth rate of 0.37 ML/s, the step convergence velocity has a decreasing exponential dependence with the temperature increase. It is determined that the single-domain surface formation velocity increases with an increase in the terrace width on the surface, which may be due to the partial participation of growth due to the formation of two-dimensional islands. Above a temperature of 650^oC, the dominant growth mode is due to the step movement and the single-domain surface formation velocity decreases with an increase in the terrace width. Thus, the single-layer step convergence is determined by both the MBE growth conditions and the Si(100) substrate orientation. The convergence of S_A- and S_B-steps of the Si(100) surface is explained by the slowdown of the step S_A-motion, which is associated with complex permeability mechanisms and a kink formation of steps. It is assumed that the reason for the slowdown of the step convergence with increasing temperature is an increase in the kink density at the S_A-step, which reduces the step S_A-permeability coefficient. Keywords:: Molecular-beam epitaxy, reflection high-energy electron diffraction, surface, terraces, steps, kinks.

In this work, the convergence kinetics investigations of the SA and SB steps on Si(100) substrates with inclination 0.5o and 0.1o were carried out. Analysis of the time dependence of reflection high-energy electron diffraction (RHEED) intensity was used to establish the growth kinetics character on vicinal Si(100) surfaces. It is shown that, in a Si flow at the growth rate of 0.37 ML/s, the step convergence velocity has a decreasing exponential dependence with the temperature increase. It is determined that the single-domain surface formation velocity increases with an increase in the terrace width on the surface, which may be due to the partial participation of growth due to the formation of two-dimensional islands. Above a temperature of 650°C, the dominant growth mode is due to the step movement and the single-domain surface formation velocity decreases with an increase in the terrace width. Thus, the single-layer step convergence is determined by both the MBE growth conditions and the Si(100) substrate orientation. The convergence of SA and SB steps of the Si(100) surface is explained by the slowdown of the step SA motion, which is associated with complex permeability mechanisms and a kink formation of steps. It is assumed that the reason for the slowdown of the step convergence with increasing temperature is an increase in the kink density at the SA step, which reduces the step SA permeability coefficient.

By molecular-beam epitaxy we have grown epitaxial layers of GaAs1-xBix solid solutions with a bismuth content of 0 < x < 0.02. Structural and optical properties of the layers were investigated. We determine the influence of the bismuth flux and substrate temperature on the bismuth incorporation into the growing layers.

By molecular-beam epitaxy we have grown epitaxial layers of GaAs1-xBix solid solutions with a bismuth content of 0 < x < 0.02. Structural and optical properties of the layers were investigated. We determine the influence of the bismuth flux and substrate temperature on the bismuth incorporation into the growing layers.

We present the results of growth of CdTe layer on (013)GaAs substrate. The sequence processes include the preparation of GaAs surface by chemical etching and annealing in ultra-high vacuum, the growth of ZnTe layer on atomically clean GaAs surface and then the growth of CdTe layer on ZnTe/GaAs. All processes were carried out without removing GaAs substrate from MBE set. The processes were controlled by RHEED and single wavelength ellipsometry. We found that the evaporation of arsenic oxides and gallium oxides from the (001)GaAs surface were observed at over 400 and 500°C, respectively. The growth of CdTe on (001)GaAs leads to appearance of mixture orientations because of large mismatch of lattice parameters. We study the growth of ZnTe on (001)GaAs and (013)GaAs substrates to prevent the growth of mixture orientations. We study the influence of cadmium and tellurium ratio in molecular fluxes and temperature on the growth mechanism of ZnTe and CdTe, crystal perfection, surface roughness and defects density. The optimal condition for growth of high quality thick CdTe on GaAs substrate were found.

The results of X-ray transmission topography and diffraction analysis of a ZnGeP₂single crystal grown by the vertical Bridgman method in the [001] direction are presented and discussed. The FWHM of rocking curves over a large area of a (100) longitudinal slice is about 12′′, which is indicative of the high quality of the examined sample. Glow discharge mass spectrometry does not show significant content of foreign chemical elements. X-ray topography reveals growth striations and dislocations. The predominant defects are single dislocations and their pile-ups. Near to the growth-axis region, curved dislocation bundles passing through the entire crystal are observed, on which precipitates are formed. In the initial part of the crystal, dislocations are located chaotically, while towards the middle of the sample they are aligned along the growth striae. In the final part of the crystal, the dislocation density increases.

Исследовано структурное состояние пленок GexSi1−x, выращенных на подложках Si вицинальной ориентации (1 1 13), отклоненной вокруг направления [11−0] на угол 6,2° от сингулярной ориентации (001). В пленках GexSi1−x содержание германия х в различных образцах составляло от 0,083 до 0,268. С помощью развитой авторами методики определения структурных параметров эпитаксиальных слоев по данным рентгеновской дифрактомерии проанализированы триклинные искажения, возникающие в кристаллической решетке пленки. Установлено, что в процессе эпитаксии решетка пленки поворачивается вокруг направления поверхностных ступеней в результате накопления в границе раздела дислокаций несоответствия, скользящих в плоскости (111). Дислокации с общим вектором Бюргерса типа а/2, не параллельным границе раздела, формируют аналог малоугловой границы. Значение угла разворота ψ прямо пропорционально плотности дислокаций несоответствия. Природа этого явления связана с уменьшением симметрии границы раздела, что приводит к изменению эффективности снятия несоответствия дислокациями, принадлежащими к разным дислокационным семействам. Рассмотрено участие этих семейств в процессе образования малоугловой границы. Для направлений [13 13 2−] и [1−10], лежащих в границе раздела (1 1 13), определены экспериментальные значения углов разворота ψ и сдвиговой деформации. Представлено сравнение экспериментальных и расчетных значений ψ для направления [13 13 2−].

The structural state of GexSi1-x films grown on Si substrates with the vicinal orientation (1 1 13) has been studied. The (1 1 13) orientation has been obtained by rotating the singular plane (001) around the [1 1 ¯0] axis. The x parameter of GexSi1-x films in different samples ranged from 0.083 to 0.268. Triclinic distortions arising in film crystal lattice have been analyzed using our technique developed for the determination of epitaxial layer structural parameters based on the X-ray diffractometry data. It has been established that during the epitaxial process the film lattice turns around the direction of surface steps due to the introduction of misfit dislocations into the interface. Dislocations with Burgers vector a/2〈110〉 which is not parallel to the interface create an analog of a tilt boundary. The turning angle value ψ is proportional to the misfit dislocation density. This phenomenon is associated with a decrease of the interface symmetry that leads to a change in the efficiency of stress relieving by dislocations belonging to different families. The influence of these families on the low-angle boundary formation is considered. Experimental values of the ψ angle and shear strain for the [13 13 2¯] and [1¯ 1 0] directions lying in the interface (1 1 13) have been defined. A comparison of the experimental and calculated values of ψ for the [13 13 2¯] direction is provided