Electrical characterization of Schottky contacts to N-polar GaN

•Schottky barrier heights were measured for various metals on N-polar GaN.•Barrier height varies linearly with metal electronegativity.•Barrier height dependence predicted by the metal-induced gap states model.•Magnitude of Schottky barrier lower for N-polar GaN compared to Ga-polar GaN.

The Schottky barrier heights of several metals (Cu, Au, Pd, Ni, and Pt) to N-polar GaN were extracted using current–voltage and capacitance–voltage measurements. The dependence of barrier height on metal was found to vary linearly with the electronegativity of the metal as predicted by the metal-induced gap states (MIGS)-and-electronegativity model. However, the magnitude of the barrier heights are lower than those predicted by the MIGS model for GaN and lower than the experimentally measured barrier heights for Ga-polar GaN. It is likely that the polarization-induced charge at the N-polar GaN surface is responsible for the reduced barrier height.