A stochastic model was developed for simulating surface growth processes during low-temperature molecular beam epitaxy. It included the dynamics of a weakly-bound physisorbed state for As. The physisorbed As was allowed to incorporate itself into the As site or Ga site (antisite), or to evaporate. The antisite As was also permitted to evaporate from the crystal surface. The As flux, temperature and growth-rate dependences of the AsGa concentration and the resultant lattice mismatch, as predicted by simulations, were in excellent agreement with experimental data. The activation energy (1.16eV) for evaporation of antisite As from the crystal, as deduced using this model, was in good agreement with theoretical estimates. At a given substrate temperature and growth rate (Ga flux), the antisite As concentration (and hence the lattice mismatch) increased with As flux in the low-flux regime and saturated at high fluxes. The critical As flux, at which the AsGa concentration and the mismatch saturated, increased with temperature. At higher temperatures, the AsGa concentration and the mismatch saturated at lower values. As the As flux increased, the coverage of the physisorbed layer increased. At a critical flux, which was dictated by the given temperature and growth rate, the coverage saturated at its maximum value of unity (complete monolayer) so that the AsGa concentration and mismatch also saturated. Lower AsGa concentrations and mismatches resulted at higher temperatures, due to a greater evaporation of AsGa from the surface of the growing crystal.

S.Muthuvenkatraman, S.Gorantla, R.Venkat, D.L.Dorsey: Journal of Applied Physics, 1998, 83[11], 5845-51