Electrostatic gating of solid-ion-conductor on InSe flakes and InSe/h-BN heterostructures

We report the electrical transport properties of InSe flakes electrostatically gated by a solid ion conductor. The large tuning capability of the solid ion conductor as gating dielectric is confirmed by the saturation gate voltage as low as ∼1 V and steep subthreshold swing (83 mV/dec). The p-type conduction behavior of InSe is obtained when negative gate voltages are biased. Chemical doping of the solid ion conductor is suppressed by inserting a buffer layer of hexagonal boron nitride (h-BN) between InSe and the solid-ion-conductor substrate. By comparing the performance of devices with and without h-BN, the capacitance of solid ion conductors is extracted to be the same as that of ∼2 nm h-BN, and the mobility of InSe on solid ion conductors is comparable to that on the SiO₂ substrate. Our results show that solid ion conductors provide a facile and powerful method for electrostatic doping.