InP Schottky contacts with increased barrier height

We present an analysis of Schottky barriers in n-InP made by incorporating a thin native oxide. An oxidation technique using nitric acid under illumination produces an oxide layer with uniform composition distribution within the layer. The growth rate is interpreted as being partially limited by diffusion presumably of oxygen through oxide. The Au Schottky barrier formed on a 40–80 Å thick oxide layer exhibits little degradation of the ideality factor n (1.04 < n < 1.10) and an increase of the barrier height by greater than 0.3 eV, resulting in at least a 10^?4 times smaller reverse leakage current density, compared with conventional Au-InP barriers. The barrier height increase is analysed by a generalised model, and is found to be produced by the existence of fixed negative charges in the oxide layer. From the present analysis, a surface state density of 6.0 × 10¹² cm^?2 eV^?1 and an equivalent surface density of negative charges of 2.8 × 10¹² cm^?2 are determined independently. The origins of these, particularly of the surface states, are considered in relation to the P vacancies at the oxide-InP interface.