Subthreshold modeling of nanoscale germanium-tin (GeSn)-on-insulator MOSFETs including quantum effects

Abstract

Although germanium-tin (GeSn) channel p-MOSFETs exhibit outstanding performance compared to other p-MOS transistors, their accurate analytical model has not yet been reported. In this paper, we present, for the first time, a 2-D surface-potential-based sub-threshold model for GeSn-on-insulator (GeSnOI) MOSFETs taking into account the interface-trapped and fixed-oxide charge densities, and also quantum effects. Unlike most of the earlier models applied to elementary and undoped semiconductor channels, the present model embraces variations in the alloy composition as well as doping concentration in the channel. Furthermore the model neither supports iterations nor involves any fitting parameters throughout the derivation, and hence it is physical, predictive, and applicable to circuit simulators like SPICE. We calculate various device parameters such as threshold voltage Vth, threshold voltage roll-up, drain induced barrier lowering DIBL and subthreshold slope SS related to short channel effects (SCEs) of GeSnOI p-MOSFETs for Sn contents ranging 0–6% and channel thickness from 5 to 10 nm. The obtained results show that the GeSnOI MOSFET with channel thickness of 5 nm yields the lowest value of Vth, DIBL, SS and Vth-shift indicating suppression of SCEs. Our model is verified by comparing analytical results for various device parameters with corresponding numerical simulation results and also with limited experimental data available in the literature.