A single gate SiGe/Si tunnel FET with rectangular HfO2 dielectric pocket to improve I on/I amb current ratio

Abstract

The ambipolar conduction in the tunnel field-effect transistors (TFETs) is considered the primary hindrance in its usage in complimentary digital circuits and low-power applications. The higher ambipolarity puts a serious question on the efficiency of a TFET, which is a result of channel/drain (C/D) tunneling. This further leads to a significant reduction in the current switching ratio (I on/I amb). This paper presents an n-type Si0.6Ge0.4/Si heterostructure TFET with a rectangular dielectric pocket (RDP) to maximize I on/I amb current ratio. This has been achieved by suppressing the ambipolarity and improving the on current simultaneously. The existence of Si1−x Gex in the source and silicon channel provides improved on current (I on) with controlled leakage current (I off). Similarly, high-k RDP in the drain reduces ambipolar current (I amb) significantly and thus, exhibits a higher I on/I amb ratio. The different parameters such as x-distance from the C/D interface, y-distance from the gate/drain interface, and dielectric constant has been considered to provide a higher I on/I amb ratio of . The effect of the presence of interface trap charges and variable Ge mole fraction has been studied. The current ratio can be further improved to with an underlap length of 25 nm.