Au, Cu, Ag, and Al are deposited on Te-doped n-GaSb layers directly grown on lattice mismatched GaAs semi-insulating substrates. Sb4/Ga beam equivalent pressure ratios are found to profoundly influence the electrical properties of the Schottky diodes investigated here. The fact that both breakdown voltage and barrier height decrease with increasing Sb4/Ga ratios is attributed to the increase in surface state densities for samples grown at higher Sb4/Ga ratios. This suggestion is further confirmed by the model of surface state densities employing the relationship of barrier height to metal work function. The surface state densities are in the range of 2.3×1014 to 1.2×1015 states/cm2/eV corresponding to Sb4/Ga ratios of 2 to 9, respectively. X-ray rocking peaks of samples grown at various Sb4/Ga ratios, and subsequently subjected to annealing, indicate different interactions at the interfaces which might support the observations.