Electrical Characterization of Pt Schottky Contacts to a-plane n-type GaN

We carried out the micro and nanoscale investigation of the electrical properties for Pt/a-plane n-type GaN Schottky contacts. Using the thermionic emission (TE) model, the temperature-dependent barrier height and ideality factor were estimated. A notable deviation from the theoretical value in the Richardson constant indicated the formation of inhomogeneous barrier heights. The thermionic field emission (TFE) model produced better fit to the experimental current-voltage data than the TE model, which suggested that the tunneling, probably due to the presence of a large number of surface defects, played an important role in the Pt/a-plane n-type GaN Schottky contacts. Two-dimensional current map of the Schottky junctions using conductive atomic force microscopy revealed an inhomogeneous spatial current distribution, which well confirmed the existence of the inhomogeneous barrier in the Schottky diodes.