Double gate n-type WSe2 FETs with high-k top gate dielectric and enhanced electrostatic control

We propose and experimentally demonstrate double-gated n-type WSe2 FETs with excellent top gate high-k dielectric layer. Under back gate control, the devices behave as n-type enhancement transistors, with ON/OFF current ratios larger than 6 orders of magnitude and a ON current close to $1\ \mathbf{pA}/\mu\mathbf{m}$ under a drain bias of 100 mV. Negative top gate biases determine a much steeper turn-on of the back gated transfer characteristic and a reduction of the hysteresis. Top gated device behaves as n-type depletion FETs, exhibiting a $I_{\mathbf{ON}}/I_{\mathbf{OFF}}$ ratio larger than 10 6 under positive bias applied to the back gate. A minimum hysteresis of 40 mV and an average subthreshold slope close to 100 mV/dec prove the high quality of the deposited top gate dielectric. The electron mobility has been extracted using the Y-function method, obtaining 22.15 cm 2 V −1 s −1 under a drain bias of 1 mV.