Transparent NiO/AZO Pseudo Ohmic Contact on P-GaN

Transparent conducting oxides, NiOx/Al-ZnO (AZO), for ohmic contacts to p-GaN were studied. NiOx /AZO films with different oxygen partial pressures and post annealing treatment were deposited on p-GaN template by pulsed laser deposition technique. To characterize the contact resistivity, transmission line method was used. One observed that as deposited AZO contact on p-GaN showed nonlinear current–voltage characteristics and, after inserting NiOx thin films between AZO and p-GaN, the ohmic characteristics was improved. The post annealing step in the oxygen environment leaded to the increased contact resistivites. As the oxygen partial pressure during the NiOx growth decreased further, contact resistivity improved more.