Unified description of ballistic and diffusive carrier transport in semiconductor structures

TL;DR

This paper develops a unified semiclassical model for carrier transport in semiconductor structures, combining ballistic and diffusive mechanisms through a thermo-ballistic current approach, and provides analytical expressions for current-voltage characteristics.

Contribution

It introduces a novel unified theoretical framework that describes both ballistic and diffusive transport in semiconductor structures within the semiclassical model.

Findings

Derived a general integral equation for reduced resistance.

Expressed current-voltage characteristics in terms of quasi-Fermi levels.

Validated the formalism with explicit simple examples.

Abstract

A unified theoretical description of ballistic and diffusive carrier transport in parallel-plane semiconductor structures is developed within the semiclassical model. The approach is based on the introduction of a thermo-ballistic current consisting of carriers which move ballistically in the electric field provided by the band edge potential, and are thermalized at certain randomly distributed equilibration points by coupling to the background of impurity atoms and carriers in equilibrium. The sum of the thermo-ballistic and background currents is conserved, and is identified with the physical current. The current-voltage characteristic for nondegenerate systems and the zero-bias conductance for degenerate systems are expressed in terms of a reduced resistance. For arbitrary mean free path and arbitrary shape of the band edge potential profile, this quantity is determined from the solution of an integral equation, which also provides the quasi-Fermi level and the thermo-ballistic current. To illustrate the formalism, a number of simple examples are considered explicitly. The present work is compared with previous attempts towards a unified description of ballistic and diffusive transport.