Reversible control of electronic transport in ionic-gel gated <i>β</i>-Ga₂O₃ thin films

Motivated by applications in power electronics, rapid progress has been made in the doping studies of β – Ga₂O₃ (BGO), although questions remain on the doping dependence of electron transport and mobility optimization at high doping densities. In this talk, we present our observations on electron transport properties of ionic – gel gated BGO films, grown via metal-organic vapor-phase epitaxy. A wide reversible voltage window of ±3 V is obtained even at 300 K for the electrostatic doping of BGO, showing the robustness of BGO with regards to unwarranted redox reactions in electrolyte gating of oxides. Temperature dependent Hall effect measurements are performed to study the doping dependence of carrier densities and mobilities in both depletion and accumulation modes. Two channel conduction model is then combined with Thomas-Fermi modelling to extract the accumulation layer carrier densities and mobilities. We have achieved an order of magnitude increase in doping densities from ~10¹⁷ cm^-3 at 0V to ~ 10¹⁸ cm^-3 at 2.5 V. Correspondingly, the 300 K mobility improves from 98 cm²V^-1s^-1 to 140 cm²V^-1s^-1, with the increase of induced electron densities. We will further discuss the scattering mechanisms limiting the electron mobility in ionic-gel gated BGO thin films.