Investigation of Ohmic contact to plasma-etched n-Al_0.5Ga_0.5N by surface treatment

We investigated the optimization effects of KOH solution treatment and SiNx sacrificial layer treatment on the contact characteristics of V/Al/Ni/Au on plasma-etched n-AlGaN. The results showed that the contacts on n-Al0.5Ga0.5N with both surface treatments are truly Ohmic in nature, while the contacts on untreated plasma-etched samples are still rectifying. Surface atomic concentration analysis revealed that both surface treatment methods effectively reduced the nitrogen vacancies on n-AlGaN induced by plasma etching, which mostly act as acceptor-like states, leading to severe compensation and hindering of the formation of Ohmic contact. Moreover, the operating voltage was reduced by 0.9 V at 20 mA for 285 nm ultraviolet light-emitting diodes, demonstrating that the surface treatment could work well for plasma-etched n-AlGaN Ohmic contacts.