Stochastic thermodynamics of a two-dimensional model of transistors

We adopt a stochastic approach to study the charge transport in transistors. In this approach, the hole and electron densities are ruled by diffusion-reaction stochastic partial differential equations satisfying a local detailed balance condition. The electric field is supposed to be concentrated in very narrow regions around the two junctions and is also approximated to be static. In this way, not only are the laws of electricity, thermodynamics, and microreversibility consistent within this approach, but also the transistor can be easily modeled as a two-dimensional system. We perform the full counting statistics of the two coupled currents and the fluctuation theorem is shown to hold. Moreover, we show that the geometric shape of the transistor exerts great influence on the transport behavior. By modeling the transistor in two dimensions, the signal-amplification factor up to about 164 can be achieved, which is comparable to the typical value of realistic transistors in the industry.