Characterization of Few layer Tungsten diselenide based FET under Thermal Excitation

Two-dimensional (2D) materials are very promising with respect to their integration into optoelectronic devices. Monolayer tungsten diselenide (WSe2) is a direct-gap semiconductor with a bandgap of ∼1.6eV, and is therefore a complement to other two-dimensional materials such as graphene, a gapless semimetal, and boron nitride, an insulator. The direct bandgap distinguishes monolayer WSe2 from its bulk and bilayer counterparts, which are both indirect gap materials with smaller bandgaps. This sizable direct bandgap in a two-dimensional layered material enables a host of new optical and electronic devices. In this work, a comprehensive analysis of the effect of optical excitation on the transport properties in few-layer WSe2 is studied. Monolayer WSe2 flakes from natural WSe2 crystals were transferred onto Si/SiO2 (270nm) substrates by mechanical exfoliation. The flakes were observed under an optical microscope. A FET based on mechanically exfoliated WSe2 was fabricated using photolithography with Molybdenum as metal contact and Silicon as back gate and the electronic properties were measured in a wide range of temperatures. The mobility of our device was found to be 0.2 cm /V-S at room temperature. The schottky barrier height was found to decrease from 80 meV to 25 meV as the gate voltage increases.