Time evolution of GaAs(111) surface morphology and desorption rate during Langmuir evaporation: Monte Carlo simulation

The high-temperature GaAs annealing kinetics is studied by Monte Carlo simulation. The evaporation rate dependences on the annealing time are obtained for (111)A and (111)B substrate surfaces in a 800-1200 K temperature range. The surface morphology evolution and evaporation kinetics are shown to be dependent on the GaAs substrate orientation. The congruent evaporation of (111)A surface corresponds to the layer-by-layer evaporation mode, while, on the (111)B surface, multilayer vacancy islands are formed. At temperatures exceeding the congruent evaporation temperature, the initial evaporation stage before the gallium droplet formation agrees with the congruent evaporation mode. The appearance of Ga droplets on the surface, corresponding to the start of incongruent evaporation regime, results in a sharp fall of the GaAs evaporation rate. It is found that the Ga droplet on vicinal surfaces locally inverts the step movement direction.