Electrolyte-gate-driven carrier density modulation and metal–insulator transition in semiconducting epitaxial CdO films

CdO has drawn much recent interest as a high-room-temperature-mobility oxide semiconductor with exciting potential for mid-infrared photonics and plasmonics. Wide-range modulation of carrier density in is both fundamental reasons (to explore transport mechanisms single samples) applications (in tunable photonic devices). Here, we thus apply ion-gel-based electrolyte gating to ultrathin epitaxial CdO(001) films, using transport, x-ray diffraction, atomic force microscopy deduce reversible electrostatic gate response from ?4 +2 V, followed by rapid film degradation at higher voltage. Further advancing the mechanistic understanding gating, these observations are explained terms low oxygen vacancy diffusivity high acid etchability CdO. Most importantly, 6-V-wide window shown enable ten-fold Hall electron density, striking voltage-induced metal–insulator transition, 15-fold variation mobility. Such modulations, which limited only unintentional doping levels exceptional voltage-tunable devices.