Evolution of GaSb epitaxy on GaAs(001)-c(4x4)

The growth of GaSb films by molecular beam epitaxy on GaAs(001)-c(4x4) at 490 degrees C has been studied in situ with scanning tunneling microscopy and ex situ with transmission electron microscopy. As the film is deposited, four distinct growth regimes are observed: the first two monolayers grow layer by layer with platelet-like two-dimensional (2D) islands; the next monolayer forms coherently strained three-dimensional (3D) quantum dots; further deposition induces film relaxation and rough 3D growth; for film thicknesses >100 nm the growth is again 2D, proceeding via spiral growth around emerging threading dislocations. The atomic-scale mechanisms inherent in the transitions between the growth regimes are discussed. Variations in growth procedures aimed at improving the quantum dot uniformity and reducing the dislocation density are proposed. (C) 1996 American Vacuum Society.