Hydrodynamic transport models for an ultrathin base Si bipolar transistor

Abstract

Hydrodynamic models for carrier transport in semiconductors can be derived by taking moments of the Boltzmann transport equation. The maximum entropy principle allows us to obtain a closed hydrodynamic model, containing no free parameters, in order to describe transport phenomena under conditions very far from thermodynamic equilibrium. Under suitable scaling assumptions, the above model reduces to the energy transport model, to the Navier-Stokes-Fourier model, or to the drift diffusion one, in which all the transport coefficients are now explicitly determined. In this paper we study the applicability of these models to an ultrathin base npn silicon bipolar transistor where the transport is quasiballistic. The validity of the constitutive equations for the fluxes and the production terms (which are the moments over the collisional operator) is investigated by using Monte Carlo simulations.