Modifications of the electronic structure of GaSb surface by chalcogen atoms: S, Se, and Te

Modifications to the electronic properties and chemical structures of the GaSb surface using the chalcogen atoms S, Se, and Te were investigated theoretically and experimentally. A self-consistent density-functional theory study indicates that an adsorption of a full monolayer coverage of chalcogen atoms on a Ga-terminated surface reduces the density of gap region states significantly. A greater photoluminescence enhancement was observed from GaSb samples treated by chalcogenide (Na2S, Na2Se, or Na2Te) in a nonaqueous than in an aqueous passivation medium. X-ray photoelectron spectroscopy reveals a Ga-rich surface after a nonaqueous passivation, with sulfidization providing a higher concentration of Ga(Sb)-chalcogen bonds than does a passivation with Na2Se or Na2Te. The uptake of chalcogen during the passivation is accompanied by the loss of surface antimony. The formation of Sb-X(X=S, Se, or Te) bonds competes with X displacing surface Sb, which dominates Se or Te incorporation in the GaSb surface lattice. The passivation kinetics was analyzed on basis of a single precursor-mediated coverage-dependent chemisorption proces. (C) 2004 American Institute of Physics.