Electrical, microstructural, and thermal stability characteristics of Ta/Ti/Ni/Au contacts to n-GaN

A metallization technique has been developed for obtaining low resistance Ohmic contact to n-GaN. The metallization technique involves the deposition of a metal layer combination Ta/Ti/Ni/Au on an n-GaN epilayer. It is observed that annealing at 750 °C for 45 s leads to low contact resistivity. Corresponding to a doping level of 5×1017 cm−3, the contact resistivity of the contact ρS=5.0×10−6 Ω cm2. The physical mechanisms underlying the realization of low contact resistivity is investigated using current–voltage characteristics, x-ray diffraction, Auger electron spectroscopy, transmission electron microscopy, and energy dispersive x-ray spectrometry.