Tunnel field effect transistor device structures: A comprehensive review

Downscaling of metal oxide semiconductor field effect transistors (MOSFET) has resulted in increased short channel effects (SCEs), off-leakage current and subthreshold swing. At room temperature, the minimum subthreshold swing for MOSFETs is 60 mV/dec. So, MOSFET is not suitable for the deep submicron regime. A new device structure is being investigated to overcome the limitations of MOSFETs. The tunnel field effect transistor is the new emerging device (TFET). TFETs are the most suitable candidate for low power applications due to their superior performance, such as low power dissipation, low leakage current, and subthreshold swing (SS) less than 60 mV/dec. Ambipolar effect is the main cause of high Ioff current, this effect can be reduced by the asymmetry in structure and varied doping in source and drain. As a result, the Ioff current in the TFET may be reduced and the Ion/Ioff current ratio can be increased. TFET is a simple p-i-n structure with reversed bias at the gate terminal and works on the principle of the band to band tunneling (BTBT). The basic structure of TFET also suffers from low Ion current. However, with the variation of physical parameters in structure, the Ion current can be improved. This paper reviews the physical parameters of TFET and their impact as well as different structures of TFET like surface tunnel transistors, p-i-n structure TFET, Junctionless TFET, and Dual gate TFETs, Heterojunction TFETs, Vertical TFETs, PNPN TFET, and Nanowire TFET.