Compact Models and the Physics of Nanoscale FETs

The device physics of nanoscale MOSFETs is related to traditional compact models. Beginning with the virtual source model, a model for nanoscale MOSFETs expressed in traditional form, we show how the Landauer approach gives a clear physical interpretation to the parameters in the model. The analysis shows that transport in the channel is limited by diffusion near the virtual source both below and above threshold, that the current saturation is determined by velocity saturation near the source, not by the maximum velocity in the channel, and that the channel resistance approaches a finite value as the channel length approaches zero. These results help explain why traditional models continue to work well at the nanoscale, even though carrier transport is distinctly different from that at the microscale, and they identify the essential physics that physics-based compact models for nanoscale MOSFETs should comprehend.