CMOS-compatible Ti/Al ohmic contacts (Rc <0.3 Ωmm) for u-AlGaN/AlN/GaN HEMTs by low temperature annealing (<450 °C)

Recently the development of CMOS-compatible fabrication technologies for GaN HEMTs has attracted increasing levels of interest [1]-[4]. A low temperature ohmic contact technology is required for gate-first device fabrication and CMOS-first GaN-Si integration process, however, typical ohmic contacts need annealing at > 800°C [1], [2]. In the past, we have reported an approach to realize low contact resistance (R_C) using CMOS-compatible metal schemes annealed at 500°C through an n⁺-GaN/n-AlGaN/GaN structure [4]. This method has a drawback that the n-doped AlGaN barrier increases the gate leakage current. In this work, we present the first low temperature (<;450°C) CMOS-compatible Ti/Al ohmic contact technology for conventional unintentionally-doped AlGaN/AlN/GaN HEMT structures.