Monte Carlo study of apparent mobility reduction in nano-MOSFETs

The concept of mobility is discussed in the case of unstrained and strained nanoscale DG MOSFET thanks to particle Monte Carlo device simulation. Without the introduction of specific scattering phenomenon for short channel devices, the apparent mobility extracted from simulated electrical characteristics decreases with the shrinking of the channel length, as experimentally observed elsewhere. We show that this reduction at room temperature is caused by non stationary effects. Moreover, both simulation results and experimental data may be well reproduced by a Mathiessen-like model, using a "ballistic mobility" extracted from MC simulations together with the usual long channel mobility.