Monte Carlo simulation of roughening at step-terraced surfaces

GaAs thermal smoothing at temperatures T ≤ 650°C under conditions close to equilibrium yields surfaces with atomically smooth terraces separated by steps of monatomic height. At higher temperatures T ≥ 700°C, surface smoothing changes to roughening. In the present paper, thermal roughening of a step-terraced surface caused by atomic step flow around step pinning centers is studied using Monte-Carlo simulation. It is proved that the Schwöbel barrier is necessary for step bunching in the presence of step pinning centers. The lower limit of the Schwöbel barrier E _S = 0.4 eV is estimated for the GaAs(001) surface. (paper)