Improvement in Schottky barrier inhomogeneities of Ni/AlGaN/GaN Schottky diodes after cumulative γ-ray irradiation

Abstract

This article reports the effect of gamma (γ)-ray irradiation on barrier inhomogeneities that leads towards improvement in diode parameters in Ni-AlGaN/GaN Schottky diodes. The Schottky diodes were subjected to a cumulative γ-ray dose up to 15 kGy and their current–voltage (I–V) and capacitance–voltage (C–V) characteristics were measured simultaneously at different temperatures during the pristine stage and after each radiation dose. The Schottky barrier height (Φ b) had an increase of 10% to 20% in the temperature range greater than 250 K. Whereas, the change in the ideality factor (η) was found to be prevalent at lower temperatures (<250 K). More linearity in the behavior of η variation with temperature was found post γ-irradiation showing an improvement in homogeneity of the metal/semiconductor interface. Post γ-ray exposure, barrier inhomogeneities at the metal/semiconductor interface were found to reduce due to annealing effects that also led towards an increase in the contribution of thermionic emission current flow. Further, a decrease of 16% in the standard deviation of the Gaussian distribution of Φ b around the mean Φ b was obtained. A decrease in contact resistance (R C) was deduced using a circular transmission line method, which was also due to the partial annealing effect of γ-ray radiation. Finally, the channel carrier concentration (n s), extracted using C–V analysis, was found to remain unaltered.