A Microscopically Accurate Model of Partially Ballistic NanoMOSFETs in Saturation Based on Channel Backscattering

We propose a model for partially ballistic metal-oxide-semiconductor field-effect transistors (MOSFETs) and for channel backscattering that is an alternative to the well-known Lundstrom model (LM) and is more accurate from the point of view of the actual energy distribution of carriers. The key point is that we do not use the concept of “virtual source.” Our model differs from the LM in two assumptions: 1) the reflection coefficients from the top of the energy barrier to the drain and from top of the barrier to the source are approximately equal (whereas, in the Lundstrom model, the latter is zero); and 2) inelastic scattering is assumed through a ratio of the average velocity of forward-going carriers to that of backward-going carriers at the top of barrier k_v >; 1 (k_v = 1 in the Lundstrom model). We support our assumptions with 2-D full-band Monte Carlo simulations, including quantum corrections in n-channel MOSFETs. We show that our model allows to extract from the electrical characteristics a backscattering coefficient very close to that obtained from the solution of the Boltzmann transport equation, whereas the LM overestimates the backscattering by up to 40%.