Multilayer low-resistance Ge/Au/Ni/Ti/Au based ohmic contact to n-GaAs

The work investigates the influence of the mode and conditions for deposition of a Ti thin film on the specific contact resistance and thermal stability of Ge/Au/Ni/Ti/Au based ohmic contacts to n-GaAs. Deposition techniques of a Ti diffusion barrier were developed in which a fifty-fold reduction in specific contact resistance was observed, and also an increase in the thermal stability of the sidewalls morphology on the edge of the contact pads. The factors influencing the specific contact resistance are: the angle at which the titanium atoms impact on the GaAs surface, the rate of deposition of the Ti film, and also the residual pressure during deposition. The factor which has an influence on the thermal stability of the sidewalls morphology of the contact pads appears to be the angle of incidence of the Ti atoms.