Impact of Quantum Confinement on Backgate-Bias Modulated Threshold-Voltage and Subthreshold Characteristics for Ultra-Thin-Body GeOI MOSFETs

Abstract

This paper investigates the impact of quantum confinement (QC) on the backgate-bias (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">bg</sub> ) modulated subthreshold and threshold-voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> ) characteristics of ultra-thin-body germanium-on-insulator (UTB GeOI) MOSFETs using an analytical solution of the Schrödinger equation verified with TCAD numerical simulation. Our study indicates that the QC effect reduces the sensitivity of the subthreshold swing to V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">bg</sub> . In addition, the sensitivity of V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> to V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">bg</sub> can be enhanced by the QC effect particularly for electrostatically well-behaved UTB MOSFETs with triangular potential well. Aside from that, the sensitivity of V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> roll-off to V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">bg</sub> is reduced by the QC effect. Since Ge and Si channels exhibit different degrees of QC due to different quantization effective mass, the impact of QC has to be considered when one-to-one comparisons between GeOI and SOI MOSFETs regarding the backgate-bias modulated threshold-voltage and sub-threshold characteristics are made. Our study may provide insights for multi-V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> device/circuit designs using advanced UTB GeOI technologies.