Surface Ordering of MBE Grown 001 Ga1−xAlxAs- A Theoretical Study

Abstract

ABSTRACTThe kinetics of MBE growth of Ga1-x.,Alx,As is studied theoretically using the stochastic model of MBE growth based on the master equation approach and the random distribution approximation. The surface ordering phenomenon during the 001 growth of Ga0.5Al0.5 As is investigated as a function of the growth conditions. The atom pair interaction energy parameters for various surface configurations were obtained from the first principle calculations. The other model parameters needed in the description of the kinetic processes are obtained from the available experimental data. The ordering kinetics is studied as a function of fluxes, flux ratio and growth temperature. The degree of ordering is estimated in terms of the short range order parameter. The short range order parameter increases with temperature till 650°K and 750°K for cation to anion flux ratios 2 : 1 and 1 : 5, respectively. Beyond this critical temperature, the short range order parameter decreases. This critical temperature is identified as the kinetic order-disorder temperature. The order-disorder phenomenon observed in this theoretical study is explained in terms of the dependence of the surface migration rate of the cations on the growth temperature. The dependence on the order-disorder temperature on the flux ratio is attributed to decreased surface migration for larger flux ratios.