Effect of KOH treatment on the Schottky barrier inhomogeneity in Ni/n-GaN

The effect of KOH treatment on the Schottky barrier inhomogeneity in Ni/n-GaN Schottky diodes was investigated. It was observed that both the barrier heights and ideality factors varied from diode to diode with a linear relationship between barrier height and ideality factor, indicating the presence of a lateral inhomogeneity in the Schottky barrier. Simple extrapolation of the straight line obtained from the linear fitting to the barrier height versus ideality factor plot to the image-force controlled ideality factor produced the lateral homogeneous barrier heights, which were higher than those from current–voltage measurements. Furthermore, Gaussian fitting to the distribution of barrier heights exhibited the increased barrier height with the smaller standard deviation after KOH treatment, implying the improved barrier homogeneity. A possible explanation for this behavior can be an improvement of the Ni/n-GaN interface intrinsic properties, e.g., through a reduction of the surface states acting as low barrier region.