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.