Forward Current Transport Mechanism and Schottky Barrier Characteristics of a Ni/Au Contact on n-GaN

The forward current transport mechanism and Schottky barrier characteristics of a Ni/Au contact on n-GaN are studied by using temperature-dependent current-voltage (T–I–V) and capacitance-voltage (C–V) measurements. The low-forward-bias I–V curve of the Schottky junction is found to be dominated by trap-assisted tunneling below 400 K, and thus can not be used to deduce the Schottky barrier height (SBH) based on the thermionic emission (TE) model. On the other hand, TE transport mechanism dominates the high-forward-bias region and a modified I–V method is adopted to deduce the effective barrier height. It is found that the estimated SBH (～0.95 eV at 300 K) by the I–V method is ～0.20 eV lower than that obtained by the C–V method, which is explained by a barrier inhomogeneity model over the Schottky contact area.