Thickness-Dependent Electrical and Optoelectrical Properties of SnSe₂ Field-Effect Transistors

Two-dimensional semiconductors such as SnSe₂ hold great promise for electronic and optoelectronic applications. Factors such as the intrinsic carrier concentration and interfacial scattering strongly influence device performance. In this study, SnSe₂-based field-effect transistors were fabricated with precise thickness control by reactive ion etching. Electrical measurements revealed that reducing the thickness from 300 to 21 nm led to an increase in carrier mobility from 3.76 to 26.6 cm² V^{− 1} s^{− 1} and an improvement in conductivity from 0.31 to 7.72 S/cm. This enhancement is attributed to a rise in carrier concentration, from 1.48 × 10¹⁸ to 1.66 × 10¹⁹ cm⁻³, along with better screening of interfacial Coulomb potential. Furthermore, the photoresponsivity varied with thickness, with thinner devices exhibiting a peak of 484 A/W under a 700-nm laser, compared to 260 A/W under a 900-nm laser for thicker devices. These findings highlight the critical role of thickness optimization in fine-tuning the electrical and optoelectronic properties of SnSe₂-based devices.