Depletion Mode MOSFET Using La-Doped BaSnO₃ as a Channel Material

The high room-temperature mobility that can be achieved in BaSnO₃ has created significant excitement for its use as channel material in all-perovskite-based transistor devices such as ferroelectric field effect transistor (FET). Here, we report on the first demonstration of n-type depletion-mode FET using hybrid molecular beam epitaxy grown La-doped BaSnO₃ as a channel material. The devices utilize a heterostructure metal-oxide semiconductor FET (MOSFET) design that includes an epitaxial SrTiO₃ barrier layer capped with a thin layer of HfO₂ used as a gate dielectric. A field-effect mobility of ∼70 cm² V^-1 s^-1, a record high transconductance value of >2mS/mm at room temperature, and the on/off ratio exceeding 10⁷ at 77 K were obtained. Using temperature- and frequency-dependent transport measurements, we quantify the impact of the conduction band offset at the BaSnO₃/SrTiO₃ interface as well as bulk and interface traps on device characteristics.