Electrical properties and microstructure of V/Al/Ni/Au contacts on n-Al0.65Ga0.35N:Si with different Au thicknesses and annealing temperatures

Abstract

We investigated the formation of ohmic contacts as a result of intermetallic phase formation between V, Al, Ni, and Au in V/Al/Ni/Au metal stacks on n-Al0.65Ga0.35N:Si. In particular, the influence of Au metal thickness and annealing temperature was analysed. The lowest annealing temperature of 750 °C for an ohmic contact with a smooth surface and a contact resistivity of about 2.4 × 10−5 Ωcm2 was achieved for V(15 nm)/Al(120 nm)/Ni(20 nm)/Au(40 nm). The lowest contact resistivity is accompanied by formation of two thin interfacial regions consisting of AlN and an Au-rich phase. We suggest that not only the formation of thin interfacial AlN layer is important for a low contact resistance, but also the formation of the Au-rich interface can have a favourable effect on the contact properties.