Low-resistance Ni/Al Ohmic contacts applied to a nonpolar a-plane n-type GaN

The authors report upon a low-resistance Ni/Al Ohmic contact to a nonpolar n-type a-plane GaN with respect to the annealing temperature. The Schottky behavior of the Ni/Al contact changes to a linear Ohmic behavior at a 700 degrees C annealing, at which the specific contact resistivity of the Ni/Al contact became as low as 5.8 X 10(-5) whereas that of a typical Ti/Al contact was 1.6 X 10(-3) Omega cm(2). This improvement is attributed to a lowering of the Schottky barrier height via a Ni-Al interdiffused layer, formed at the interface between the metal and the nonpolar a-plane n-type GaN during the annealing process. (C) 2011 American Institute of Physics. [doi:10.1063/1.3579252]