Validation of an extended hydrodynamic model for a submicron npn bipolar junction transistor

The validity of the constitutive equations for the fluxes and the production terms, obtained by means of the maximum entropy principle, and the hyperbolicity conditions are checked with direct simulation Monte Carlo. We verify numerically that the quadratic closure is more accurate with respect to the zero-order one, but some irregularities can appear in the solution due to the loss of hyperbolicity in some regions of the device.