DEVELOPMENT OF THE NA GAAS(111)A-(2X2) INTERFACE AT ROOM AND LOW-TEMPERATURE/

The alkali-metal/III-V semiconductor interface is a model system with which to study overlayer metallization and Schottky barrier developmen t. Until now, typically the cleaved (110) surfaces of the semiconducto r have been utilized in this respect, though in this work we have used the Ga-vacancy (2 x 2) reconstructed surface of GaAs(111)A as the sta rting surface. This surface is known to exhibit many similarities with the cleaved (110) surface, due to the separation of empty and filled dangling bonds onto the Ga and As surface atoms respectively. We have found through using soft X-ray photoemission from both core-level and valence-band features that the interface is remarkably unreactive, wit h almost no change in the Ga 3d lineshape with Na deposition at low te mperatures. With regard to the growth-mode, work-function variation an d band-bending however, the behaviour is close to that found for the c leaved surface. The onset of the Na LVV Auger transition only occurs a fter metallization begins and is consistent with ionic bonding to the substrate, though the substrate core-level development points to a red uced charge transfer with respect to the (110) surface.