A simulation study of the influence of a high-k insulator and source stack on the performance of a double-gate tunnel FET

The influence of incorporating HfO₂ as a dielectric at the drain side and a silicon stack at the source side on the electrical performance of a double-gate tunnel field-effect transistor (TFET) is investigated by comparing a conventional TFET structure with four other structures in which the gate dielectric material is either homogeneous or heterogeneous while the insulator on the drain side is either SiO₂ or HfO₂. Moreover, a structure with a silicon source stack is proposed and the figures of merit of the resulting device are compared with other counterparts. The results of the simulations reveal that the presence of an HfO₂ insulator on the drain side reduces the ambipolar conduction while the heterogeneous gate dielectric enhances the drive current and transconductance. However, the use of HfO₂ slightly deteriorates the source–gate and drain–gate capacitances in comparison with the conventional TFET. Furthermore, the incorporation of a silicon source stack along with a heterogeneous gate dielectric and HfO₂ insulator on the drain side leads to a higher I_ON/I_OFF ratio, lower subthreshold slope (S), and lower ambipolar conduction in the studied TFET with channel length of 50 nm.