Plasma-assisted surface treatment for low-temperature annealed ohmic contact on AlGaN/GaN heterostructure field-effect transistors

Abstract

In this study, a low-temperature annealed ohmic contact process was proposed on AlGaN/GaN heterostructure field effect transistors (HFETs) with the assistance of inductively coupled plasma (ICP) surface treatment. The effect of ICP treatment process on the 2DEG channel as well as the formation mechanism of the low annealing temperature ohmic contact was investigated. An appropriate residual AlGaN thickness and a plasma-induced damage are considered to contribute to the low-temperature annealed ohmic contact. By using a single Al layer to replace the conventional Ti/Al stacks, ohmic contact with a contact resistance of 0.35 Ω·mm was obtained when annealed at 575 °C for 3 min. Good ohmic contact was also obtained by annealing at 500 °C for 20 min.