Observation of different transport behaviors in a two-dimensional MoTe2 field-effect transistor with engineered gate stack

Abstract

Back-gate field-effect transistor (FET) fabricated from exfoliated two-dimensional (2D) materials have been widely applied on the electronic device applications of the novel transition metal dichalcogenides (TMDs) since their experimental discovery. Si substrate covered with thick SiO2 dielectric layer is commonly used due to the natural back-gate geometry and good optical contrast which, however, lacks sufficient gate control over the ultra-thin channel because of the thick dielectric. Here, in this work, we report a high-performance back-gate MoTe2 FET fabricated on a novel Al2O3/ITO (indium tin oxide)/SiO2/Si stack substrate. The stack thickness has been carefully designed and engineered to enhance the gate control of the MoTe2 channel while enabling sufficient optical contrast between the substrate and the exfoliated 2D flakes. Unipolar and ambipolar transport behaviors on different substrates have been observed and analyzed. As compared to the conventional 300 nm SiO2/Si substrate, the MoTe2 FET on the engineered gate stack has exhibited higher on/off current ratio with smaller cut-off current and smaller subthreshold slope of 126.57 mV/dec. These results are attractive in building novel logic devices based on the 2D MoTe2 with unipolar and ambipolar behavior broadening the applications in advanced nanoelectronics and optoelectronics systems