We carried out microscale and nanoscale investigations of the electrical properties of Pt/a-plane n-type GaN Schottky contacts. Using the thermionic emission (TE) model, we observed that both the barrier heights and ideality factors varied from diode to diode with a linear relationship between them, indicating a spatial fluctuation of barrier height. The thermionic field emission (TFE) model produced a better fit to the experimental current-voltage data than the TE model, which suggested that 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. A two-dimensional current map of the Schottky junctions using conductive atomic force microscopy revealed an inhomogeneous spatial current distribution, which confirmed the existence of an inhomogeneous barrier in the Schottky diodes.