Optical and electronic characterization of transition layer in thin film Au-GaAs Schottky barrier

Abstract

The possibility of determination of optical parameters and thickness of interfacial oxide (IO) layer by multiple-angle-of-incidence (MAI) ellipsometry has been studied for Au-IO-GaAs structures with different oxide thickness. The films parameters have been calculated by the original program of inverse ellipsometric problem solution. Parameters of oxide layer have been determined both for free GaAs surface and for that covered by Au film. Gold film was prepared by vacuum evaporation on the heated n-n+GaAs substrate. Its parameters have been determined by MAI ellipsometry and transparency measurements of Au-quartz satellite system. The investigation showed the change of optical parameters of GaAs oxide layer after the Au evaporation. In the assumption of invariable thickness of IO layer its optical parameters are : n = 1.0±0.1, k = 0.4 ÷ 0.6. The mechanism of current transport and electrical parameters of Au-IO-GaAs structures have been determined from I-V and C-V characteristics of Schottky diodes. The results of the determination of transition layer thickness to its dielectric constant ratio (d\\εi)) from electrical characteristics of barrier also indicate its difference from initial parameters of oxide layer probably due to interdiffusion of Au, Ga, and As.