New experimental insight into ballisticity of transport in strained bulk MOSFETs

Abstract

This paper proposes a new expression unifying all transport mechanisms (drift-diffusion, velocity-saturation and quasi-ballistic). This enables an experimental extraction of the limiting velocity and also, for the first time, a determination of its nature (thermal injection or velocity saturation). We show that the observed increase in the limiting velocity in short and strained devices was confusingly interpreted as an evidence of increasing ballisticity. At least down to 20nm channel length, the transport remains velocity-saturation limited. However, the good news we confirm experimentally is that V sat increases itself in short and strained devices. This promises an increase Ion, even if the nature of the transport is velocity-saturated. This new findings open doors for the study and optimization of transport in advanced CMOS technologies.