Applicability of Macroscopic Transport Models to Decananometer MOSFETs

We perform a comparative study of various macroscopic
transport models against multisubband Monte Carlo (MC)
device simulations for decananometer MOSFETs in an ultrathin
body double-gate realization. The transport parameters of
the macroscopic models are taken from homogeneous subband
MC simulations, thereby implicitly taking surface roughness and
quantization effects into account. Our results demonstrate that the
drift-diffusion (DD) model predicts accurate drain currents down
to channel lengths of about 40 nm but fails to predict the transit
frequency below 80 nm. The energy-transport (ET) model, on
the other hand, gives good drain currents and transit frequencies
down to 80 nm, whereas below 80 nm, the error rapidly increases.
The six moments model follows the results of MC simulations
down to 30 nm and outperforms the DD and the ET models.