In this work, the structural and electrical properties of Ti/Al/Ni/Au contacts on n-type
Gallium Nitride were studied. An ohmic behaviour was observed after annealing above 700°C. The
structural analysis showed the formation of an interfacial TiN layer and different phases in the
reacted layer (AlNi, AlAu4, Al2Au) upon annealing. The temperature dependence of the specific
contact resistance demonstrated that the current transport occurs through thermoionic field emission
in the contacts annealed at 600°C, and field emission after annealing at higher temperatures. By
fitting the data with theoretical models, a reduction of the Schottky barrier from 1.21eV after
annealing at 600°C to 0.81eV at 800°C was demonstrated, together with a strong increase of the
carrier concentration at the interface. The reduction of the contact resistance upon annealing was
discussed by correlating the structural and electrical characteristics of the contacts.