Core-shell type of tunneling nanowire FETs for large driving current with unipolarity

Abstract

A radial-heterojunction (HJ), as opposed to axial-HJ, tunneling-FET (tFET) is proposed to increase the driving current as much as 4 times while maintaining steep subthreshold swing (SS) and non-ambipolarity (i.e., unipolar transfer characteristics). The core/shell nanowire is adopted for the bulk of the device, with source region in the core of the wire and shell for the channel. The tunneling thus occurs in the radial direction, increasing the junction area substantially and leading to large on current. The core-shell junction is made of Ge-Si, and a lightly-doped drain-extension is used to suppress ambipolarity, which impedes the application of many types of tunneling devices in digital circuits. Comparison with unipolar axial-HJ GAA NW-tFET is made to show the advantage of the radial structure.