MBE growth of compound semiconductors: Part II. Applications of the stochastic model
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In this part of the work (Part II), two typical applications of the stochastic model to the MBE growth kinetic studies are presented. The applications are the MBE growth kinetics of a hypothetical compound semiconductor, ab, and diamond cubic alloy, ax. In this study, the effect of the surface diffusion process on the MBE growth kinetics is analyzed. In the case of the compound, ab, the results of the present stochastic model are compared with that of a Monte Carlo simulation study in the temperature range of 600-850 K. The results of the two studies agree qualitatively. Higher substrate temperatures result in higher growth rate and growth front smoothness due to higher surface diffusion. Beyond 800 K, the growth rate and the growth front smoothness become independent of temperature because of the saturation of the interlayer diffusion process. In the case of the alloy studies, the kinetics of a hypothetical diamond cubic alloy in which the thermodynamics favors phase separation, is studied in the temperature range of 573-898 K. Below 648 K, due to negligible surface diffusion, there is no clustering of the alloy, but the surface roughness is very large. In the intermediate temperature range of 573-798 K, with increasing temperature, the surface diffusion increases, resulting in more clustering and less surface roughness. Above 798 K, due to very high surface diffusion, complete phase separation of the alloy and a smooth surface result. I. INTRODUCTION
monoatomic. The author's own Monte Carlo code was used for the study.
With the advent of the ultra high vacuum crystal growth technique of Molecular Beam Epitaxy (MBE) for the growth of compound semiconductors, there is a surge in the research activity to understand the growth kinetics, experimentally and theoretically.1 The theoretical studies are based on the MC simulations. In this manuscript, two typical applications of the stochastic model developed in Part I to the MBE growth kinetics are presented. Application I is presented in Sec. II where the kinetics of growth of a typical ab compound is considered and the results of the study are discussed. Application II is presented in Sec. Ill where the MBE growth kinetics of a hypothetical ax diamond cubic alloy is considered and the results of the study are discussed. In Sec. IV, a discussion of the two studies along with the limitations of the present stochastic model are presented. Conclusions are presented in Sec. V.
The model parameters for the system are chosen based on the GaAs system. It is noted that even though the parameters are based on the GaAs system, the kinetic model employed is different from that of the GaAs system. Details of the differences between the kinetics of the GaAs system and the present model are presented in the discussion section. Model parameters were obtained for this study using Eqs. (16)-(20) of Part I and the growth and material data based on the GaAs system. Growth conditions and material parameters employed are listed in Table I. Using these parameters in Eqs. (16)-(20) of Part
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