Demonstration of GaN HyperFETs with ALD VO2

Owing to strong electron-electron interactions, transition metal oxide materials can exhibit multiple phases with vastly different electronic, magnetic, structural, and thermal properties. Reversible control of the transitions between these phases by electronic means can give rise to completely novel devices which can provide new functionalities and help to overcome limits of traditional semiconductor devices [1, 2]. VO2 is a transition metal oxide material that exhibits a metal-insulator transition (MIT) at a temperature of ~67 C [3]. Recently, by coupling VO2 to the source of traditional semiconductor MOSFET devices, hybrid-phase-transition-FET (hyper-FET) devices were demonstrated [4]. These HyperFETs showed steep switching slope less than the room-temperature Boltzmann switching limit of ~60 mV/dec [4]. GaN based electronics has emerged as an enabler of high-speed and high-power RF and microwave electronics [5], and is currently being investigated intensively for next-generation high-voltage power electronics [6,7], as well as steep-switching based low-power digital electronics [8]. In this work, we combine ALD-grown VO2 with III-Nitride high-electron mobility transistors (HEMTs) to realize GaN-VO2 HyperFETs, demonstrating steep-switching behavior in a platform that is amenable to integration and scaling.