Abstract: Metal‐induced extrinsic surface states on Si, Ge, and GaAs

Abstract

During the chemisorption and subsequent metal film growth of Al, Ga and In atoms on (111) surfaces of Si, Ge, and GaAs we observed a large decrease in the signals from both occupied and unoccupied intrinsic surface states. Extrinsic surface states, which were coverage dependent, were observed in the range 0–2 eV below the valence‐band maximum EV. The change in the surface potential and band bending were monitored using uv photoemission spectroscopy (UPS) of bulk direct transitions. About 2/3 to 3/4 of the change in band bending occurred during the first monolayer of metal chemisorption. Unoccupied surface states in the energy band gap were monitored using electron energy‐loss spectroscopy (ELS) from core levels to empty surface and conduction‐band states. This technique is essentially the same measurement as the photoelectron‐yield spectroscopy reported by Eastman but has lower energy resolution and greater surface sensitivity. On all (111) surfaces we observe a decrease in intrinsic surface states with m...