Bandgap Extraction and Device Analysis of Ionic Liquid Gated WSe2 Schottky Barrier Transistors

Through the careful study of ionic liquid gated WSe2 Schottky barrier field-effect transistors as a function of flake thickness—referred to in the following as body thickness, tbody—critical insights into the electrical properties of WSe2 are gained. One finding is that the inverse subthreshold slope shows a clear dependence on body thickness, i.e., an approximate square root dependent increase with tbody, that provides evidence that injection into the WSe2 channel is mediated by thermally assisted tunneling through the gate-controlled Schottky barriers at the source and drain. By employing our Schottky barrier model, a detailed experimental plot of the WSe2 bandgap as a function of body thickness is obtained. We will discuss why the analysis employed here is critically dependent on the use of the above-mentioned ionic liquid gate and how device characteristics are analyzed in detail.