The microscopic details of Ga adatom diffusion upon an As-stabilized (001) surface were investigated by using an  ab initio  pseudopotential method. The results showed that Ga adatoms diffused on the surface by passing through the missing As dimer rows. A comparison with scanning tunnelling microscopic experiments during molecular beam epitaxial growth suggested that a low pressure of As increased surface Ga adatom diffusion due to the creation of a continuous Ga adatom diffusion path. This conclusion was consistent with the observation that low-temperature growth was possible via migration-enhanced epitaxy in which As and Ga sources were supplied alternately.

K.Shiraishi: Applied Physics Letters, 1992, 60[11], 1363-5