A microstructural and electrical investigation of Pd/Ge/Ti/Au ohmic contact to n-type GaAs

Abstract

Interfacial microstructure and elemental diffusion of Pd/Ge/Ti/Au ohmic contact to n-type GaAs have been investigated using x-ray diffraction(XRD), Auger electron spectroscopy(AES), and cross-sectional transmission electron microscopy(XTEM), and their results are used to interpret the electrical properties. The lowest contact resistance of 0.43 Omega mm is obtained after annealing at 380 degrees C. The contact is thermally stable even after isothermal annealing for 5h at 400 degrees C. The good Pd/Ge/Ti/Au ohmic contact is due to the formation of both AuGa and TiO compounds. The AuGa compound enhances the creation of more Ga vacancies, followed by incorporation of Ge into Ga vacancies and TiO compound suppresses As outdiffusion from GaAs substrate, respectively.