High Performance, Ultra-thin, Strained-Ge, Heterostructure FETs With High Mobility And Low Leakage

Abstract

High mobility channel materials are very promising for enhanced transport in future nanoscale MOSFETs. However, because of their reduced bandgap, large Band-To-Band Tunneling (BTBT) leakage currents can ultimately limit the scalability of FETs incorporating high mobility (small bandgap) channels. For the first time, the tradeoffs between drive current (ION), intrinsic delay (τ), band-to-band tunneling (BTBT) leakage and short channel effects (SCE) have been systematically compared in futuristic high mobility materials, like strained-Si, strained-SiGe and relaxed-Ge. The optimal channel materials and device structures for nanoscale p-MOSFETs are discussed through detailed BTBT (including band structure and quantum effects), Full-Band Monte-Carlo, 1-D Poisson-Schrodinger simulations. We present a novel, Heterostructure FET, which can significantly reduce the off-state leakage currents, while retaining its high mobility, making it suitable for scaling into the sub-20nm regime. Through detailed experiments, we examine the enhanced transport and low leakage in ultra-thin, strained-Ge, heterostructure MOSFETs on bulk-Si and UT-SOI.