Self-consistent analysis in the presence of phase-randomizing processes for double-barrier structures

We present a model, based on the nonequilibrium retarded Green’s function method of the quantum kinetic (Keldysh) theory, that describes carrier transport in three-dimensional quantum structures with translational invariance in the transverse direction. The transport equations include inelastic phase-breaking processes and describe the transport of both the coherent and incoherent electrons within the same framework with a set of first-order coupled linear differential equations. These equations can be solved without resorting to evaluating the Green’s function. The model accounts for local space charges in Poisson’s equation and is suitable for modeling the steady-state current-voltage characteristics of double-barrier structures. A realistic model for these devices should include the effects of inelastic processes and space charge simultaneously. However, as an illustration, we present numerical results for double-barrier devices by assuming that the electrons undergo elastic phase-breaking collisions only. Our simulation results show that the accumulated space charge is a function of phase-breaking collision and that the presence of dissipation within the contacts is partly responsible for the low observed peak-to-valley current ratio.