Theoretical investigations of initial growth process on GaAs(001) surfaces

This paper briefly reviews our latest achievements in theoretically approaching the initial growth process including adatom migration and changes in the atomistic structure on the GaAs(001)-(2 x 4) surface. The calculations are performed using the ab initio pseudopotential method, empirical interatomic potential and Monte Carlo (MC) simulation. On the (2 x 4)beta 1 surface, we found that Ga adatom migration strongly depends on the Ga adatom coverage during molecular-beam-epitaxy growth. This can be interpreted by the electron counting model. Based on these findings, migration potentials near the steps on the (2 x 4)beta(2) surface can be successfully calculated using a simple energy formula. Using this energy formula, the newly developed electron-counting MC simulation results imply that the GaAs(001) surface changes its atomic arrangement from an initial (2 x 4)beta(2) to (2 x 4)beta 1 via (2 x 4)alpha. Further Ga and As adsorptions fill up the lattice sites in the missing dimer region continuing layer-by-layer growth. (C) 1997 Elsevier Science B.V.