Quantum mechanical analysis of 2D transition metal dichalcogenide material based vertical heterojunction tunnel FET

In this work, a single layer n-doped MoS2 and p-doped WTe2 based vertical heterojunction tunnel FET has been investigated through a well-organized quantum mechanical approach. The key outcome is the design criteria of the device for low subthreshold swing keeping its length as short as possible. Inter-coupled real space model Hamiltonian of the device is formed by introducing the coupling energy of the WTe2 valence band and the MoS2 conduction band in the overlap region. Here, MATLAB based self-consistent analysis is used to numerically solve the device by coupling Schrodinger and Poisson equations taking into account the plane dependence of permittivity in 2D transition metal dichalcogenide materials. For 15 nm channel overlap length and 15 nm gate extension length, a subthreshold slope of as low as 10 mV/decade has been obtained. For 20 nm channel overlap length, an ON current of 18 mu A/mu m has been obtained as well. The effect of the top gate extension, overlap length, and dielectric layer thickness over the ON and OFF state currents has been explained from the viewpoint of device physics. Thus, the framework presented will help designers to optimize the device for improved performance.