Wide Range Reversible Transport Modulation and Electron Density Dependence of Mobility in Ion-Gel-Gated BaSnO₃ Films

Rapid progress has been made with BSO films since the report of room temperature mobility >300 cm²V^-1s^-1 in bulk crystals. Questions remain over mobility-limiting mechanisms, however. Here we report doping-dependent electronic transport in epitaxial-BSO-based electric double layer transistors using ion gel electrolytes. Over an exceptional gate voltage window of -3 to +4 V, at 300 K, electrostatic gating mechanisms dominate, supported by reversible transport response and operando synchrotron X-ray diffraction experiments. This is in stark contrast with many complex oxides and, vitally, is attributed here to the exceptionally small diffusivity of oxygen vacancies in BSO. Wide-range voltage control of resistance is demonstrated in a series of undoped and initially chemically n-doped BSO films, including a strong to weak localization crossover. Interfacial electron density (n) and mobility (µ) are extracted from two-channel conduction modelling and the µ-n relation is probed from ~10¹⁸ cm^-3 to >10²⁰ cm^-3. Universally, µ increases rapidly with n before decreasing above ~10²⁰ cm^-3, potentially due to surface scattering. The highest µ achieved is 140 cm²V^-1s^-1 in La-doped BSO films by increasing µ with gating by up to 55%.