Electrical Properties of Ti/Al Ohmic Contacts to Sulfur-Passivated N-Face n-Type GaN for Vertical-Structure Light-Emitting Diodes

We investigate the electrical properties of Ti/Al ohmic contacts on -passivated N-face n-GaN:Si grown by molecular beam epitaxy. It is shown that the passivation results in an increase in the photoluminescence intensity of n-GaN. Current–voltage measurements show that the passivated samples experience a slight degradation in the electrical properties upon annealing at , while the untreated samples show some improvement although still nonohmic. Based on the and X-ray photoemission spectroscopy results, we describe the possible mechanisms for the passivation and annealing dependence of the electrical properties of the Ti/Al contacts to the N-face n-GaN.