KINETIC INSTABILITY IN THE EPITAXIAL-GROWTH OF SEMICONDUCTOR SOLID-SOLUTIONS

The epitaxial growth of a semiconductor solid solution is considered. Migration of adsorbed atoms on the surface consists of diffusion and d rift in the long-range elastic potential created by composition fluctu ations in all completed monolayers. The process of migration is descri bed by the continuity equation for diffusion and drift. It is shown th at for temperatures lower than a certain critical temperature T-c, str ain-induced drift dominates diffusion. Then there exists a mode of sol id solution composition fluctuations whose amplitude increases with th e monolayer's number. This increase implies that the growth of a spati ally homogeneous solid solution is kinetically unstable. The two-dimen sional wave vector of the corresponding unstable mode may be of an arb itrary direction which is governed by the interplay of drift and diffu sion. In contrast to the effect of long-range elastic forces on the th ermodynamic instability of solid solutions, where the elastic forces h inder the phase separation, these forces favor kinetic instability and increase the critical temperature T-c. The theory is developed for th e particular step-flow growth of the solid solution on a surface vicin al to the (001) surface of a cubic substrate.