Modeling tunnel field effect transistors - from interface chemistry to non-idealities to circuit level performance

TL;DR

This paper develops a comprehensive quasi-analytical model for TFETs that incorporates microscopic interface chemistry, non-idealities, and circuit-level performance metrics, validated against quantum transport calculations.

Contribution

The paper introduces a novel quasi-analytical model for TFETs that integrates interface chemistry, non-idealities, and first-principles calibration, enabling detailed performance analysis.

Findings

Model accurately predicts ballistic tunneling current.

Interface trap-assisted tunneling and Auger processes significantly affect off-state behavior.

Model can quantify the impact of interface quality on device performance.

Abstract

We present a quasi-analytical model for Tunnel Field Effect Transistors (TFETs) that includes the microscopic physics and chemistry of interfaces and non-idealities. The ballistic band-to-band tunneling current is calculated by modifying the well known Simmons equation for oxide tunneling, where we integrate the Wentzel-Kramers-Brillouin (WKB) tunneling current over the transverse modes. We extend the Simmons equation to finite temperature and non-rectangular barriers using a two-band model for the channel material and an analytical channel potential profile obtained from Poisson's equation. The two-band model is parametrized first principles by calibrating with hybrid Density Functional Theory calculations, and extended to random alloys with a band unfolding technique. Our quasi-analytical model shows quantitative agreement with ballistic quantum transport calculations. On top of the ballistic tunnel current we incorporate higher order processes arising at junctions coupling the bands, specifically interface trap-assisted tunneling and Auger generation processes. Our results suggest that both processes significantly impact the off-state characteristics of the TFETs - Auger in particular being present even for perfect interfaces. We show that our microscopic model can be used to quantify the TFET performance on the atomistic interface quality. Finally, we use our simulations to quantify circuit level metrics such as energy consumption.