Influence of annealing effects on the electrical and microstructural properties of Se Schottky contacts on n-type GaN

The electrical and microstructural properties of Se/n-gallium nitride (GaN) Schottky diode have been investigated by current-voltage (I-V), capacitance-voltage (C-V) and transmission electron microscopy (TEM) measurements as a function of annealing temperature. The Se/n-GaN Schottky contact exhibited an excellent rectification behavior. The barrier height of the as-deposited Se/n-GaN Schottky contact is 0.94 eV (I-V) and 1.55 eV (C-V), respectively. However, the barrier height of Se/n-GaN Schottky diode decreases to 0.90 eV (I-V) and 1.33 eV (C-V) upon annealing at 200 °C. Cheung's and modified Norde functions are employed to determine the barrier height and series resistance. TEM results reveal that the Se film becomes fully crystallized for the contact annealed at 200 °C compared to the as-deposited contact without the reaction between Se film and GaN substrate. It is observed that the barrier height of Se/n-GaN Schottky diode decreases with increasing annealing temperature. This could be associated with the decrease in series resistance caused by the phase transformation from high resistance amorphous Se to low resistance crystalline Se. Further, the interface states density is found to be increased with the increasing annealing temperature. The Schottky emission mechanism is found to dominate the reverse leakage current in Se/n-GaN Schottky diodes irrespective of annealing temperatures.