Effect of Ar‐Based Reactive Ion Etching on the Ohmic Contacts in Gallium Oxide Field Effect Transistor

Abstract

Herein, ultra‐wideband gap semiconductor β‐gallium oxide (β–Ga2O3) over sapphire ( orientation) is investigated for ohmic contact improvement with the help of argon (Ar)‐based reactive ion etching (RIE). Postannealing effects of these contacts over ( orientation) gallium oxide samples are also investigated. The surface defects and oxygen vacancies generated by Ar etching lead to the formation of as‐deposited ohmic contacts with the Ti/Au metal stack. A contact resistance of 10.52 Ω mm with a specific contact resistivity of 2.24 × 10−4 Ω cm2 is achieved with 10 min Ar RIE prior metallization. However, the contacts further degrade when samples are subjected to annealing. The electrical measurements and energy‐dispersive X‐ray spectroscopy elemental mappings at samples after annealing reveal that it is due to the formation of titanium oxide (TiOx) compound which acts as an insulator and concurrent with the out‐diffusion of Ga and in‐diffusion of gold. These results show the impact of anisotropy of gallium oxide over different annealing temperatures. These results and techniques may pave the way for better ohmic contacts for gallium oxide‐based high‐voltage and high‐power applications.