INTERACTION OF GASE WITH GAAS(111) - FORMATION OF HETEROSTRUCTURES WITH LARGE LATTICE MISMATCH

We have studied the epitaxial growth of GaSe, a layered van der Waals material, on GaAs, a zinc-blende-structure semiconductor. This heteros tructure exhibits a 6% lattice mismatch, and is a prototypical example of van der Waals epitaxy, where the weak van der Waals interaction al lows the misfit to be accommodated without the formation of electronic ally active defects. GaSe was supplied to the growing surface from a s ingle GaSe Knudsen cell. Reflection high energy electron diffraction a nd x-ray photoemission spectroscopy studies of the nucleation of GaSe indicate Se reacts with the GaAs surface to remove the surface danglin g bonds prior to GaSe formation. This is followed by the oriented grow th of stoichiometric GaSe layers, that are rotationally aligned with t he underlying GaAs substrate. The termination of the GaAs dangling bon ds most likely occurs by Se substitution for As in the surface layer o f GaAs(lll) B and by direct bonding of Se to surface Ga on GaAs(lll) A surfaces. In addition, photoemission measurements indicate that the s ubsurface Se uptake into the GaAs(lll) A lattice is higher than that i n the (111) B lattice. (C) 1998 American Vacuum Society.