Germanium-source germanium-channel silicon-drain vertical TFET for low power applications

Abstract

Scaling problems associated with the MOSFET calls for other novel devices which can outperform MOSFET at nanometer dimensions. As device dimensions shrink, various tunneling leakage factors in the MOSFET increase due to non-scalable junction electric fields. Devices based on tunneling currents can be effectively used as a solution to this problem. In this paper, a novel concept of a particular type of tunnel field effect transistor (TFET) with gate controlled band to band tunneling as its working principle is presented and it is observed that a germanium source-germanium channel-silicon drain TFET is able to provide better on current to off current ratios compared to a silicon TFET thus enabling efficient operation at low supply voltage and power. In this work, the TFET structure is studied and design parameters are optimized based on theory and simulation results to have high on current to off current ratio. Synopsis® device simulation tool MEDICI® is used for the simulations.Index Terms-tunnel field effect transistor, tunneling leakage, band to band tunneling

Electrical characteristics of tunneling field-effect transistors with asymmetric channel thickness

“…The Si-based TFET has lower on-current due to large Si energy band which makes it difficult to align the conduction band of the channel and the valence band of the source. Indeed, germanium-source TFET with small energy band gap has been proposed [25][26][27] to solve the problem of the low on-current level. In addition, the QC effect considerably reduces the on-current because of the discreteness of the sub-band energy levels in the QC.…”