We present a study of the giant piezoresistance effect in p-type silicon using full-band Monte Carlo simulation based on 30-band k.p calculation. This effect has been demonstrated experimentally in Si nanowires by He and Yang. By including the well-known strain effect on the band structure, and by introducing a law of variation of the surface potential according to the applied mechanical stress, we can reproduce this effect. This variation of surface potential modulates the depletion depth and then the conductivity of the structure. This modulation induces a strong variation of the total amount of carriers available for the conduction, which increases drastically this piezoresistive effect. This is probably the main origin of this effect, which may be used to achieve high performance MEMS sensors.

To study the thermal effect in nano-transistors, a simulator based on the self-consistent solution of the Boltzmann transport equations (BTEs) for both electrons and phonons has been developed. It has been used here to investigate the self-heating effect in a 20-nm long double gate MOSFET. In this model, a Monte Carlo (MC) solver for electrons has been coupled with a direct solver for the phonon transport. This method is particularly efficient to provide a deep insight on the out-of-equilibrium thermal dissipation occurring at the manometer scale when the length of the devices is smaller than the mean free path of both charge and thermal carriers. This approach allows us to evaluate accurately the phonon emission and absorption spectra in both real and energy spaces.