Characterization of electrical and optical properties of indium selenide nanosheet

Abstract

Indium selenide (InSe) is an attractive two-dimensional semiconducting material due to its high electron mobility (> 1000 cm^2/Vs at room temperature (RT)) and outstanding photo-responsivity (~ 12.3 A/W under 450 nm wavelength light illumination). However, in spite of these superior performances, intrinsic transport property studies of InSe are still insufficient. Here, we investigated electrical and optical characteristics of high-mobility InSe nanosheet FETs, which were encapsulated by hexagonal boron nitride to improve the air stability and to reduce the charged impurity scattering by the substrate. Furthermore, few-layer graphene was employed as a contact material to prevent InSe from being damaged by the conventional metal deposition and to achieve very clean interfaces at the junction of contacts, leading to the low Schottky barrier height. Using the four-probe methodology, the conductivity, the resistivity, and the electron mobility of InSe were measured as a function of temperature (T) and carrier density (n). Our InSe nanosheet FETs exhibit a high electron mobility (μ) exceeding 840 cm^2/Vs at T = 300 K and n = 1.5 × 10^12 cm^-2. In particular, by fitting resistivity data using Bose-Einstein distribution, we analyzed the resistivity and the limited mobility by phonon scattering and impurity scattering. In our InSe FETs, at low temperature, impurity-limited mobility (2110 cm^2/Vs) is independent to the carrier density, indicating the short-range impurity is dominant impurity. Besides, we extracted the intrinsic phonon-limited mobility of 1260 cm^2/Vs at RT and 15500 cm^2/Vs at 100K. Furthermore, photocurrents of InSe heterostructures with visible wavelength light illumination are measured to analyze optical properties of InSe nanosheet. In conclusion, we expect that this results will be help to understand and realize further InSe based devices and applications.