Effects of Sb₄/Ga ratios on the electrical properties of GaSb Schottky diodes

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.