SnSe(2) Field-Effect Transistor with High On/Off Ratio and Polarity-Switchable Photoconductivity

SnSe(2) field-effect transistor was fabricated based on exfoliated few-layered SnSe(2) flake, and its electrical and photoelectric properties have been investigated in detail. With the help of a drop of de-ionized (DI) water, the SnSe(2) FET can achieve an on/off ratio as high as ~ 10(4) within 1 V bias, which is ever extremely difficult for SnSe(2) due to its ultrahigh carrier density (10(18)/cm(3)). Moreover, the subthreshold swing and mobility are both improved to ∼ 62 mV/decade and ~ 127 cm(2) V(−1) s(−1) at 300 K, which results from the efficient screening by the liquid dielectric gate. Interestingly, the SnSe(2) FET exhibits a gate bias-dependent photoconductivity, in which a competition between the carrier concentration and the mobility under illumination plays a key role in determining the polarity of photoconductivity. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s11671-019-2850-0) contains supplementary material, which is available to authorized users.