The inclusion of a finite capture time in the numerical simulation of quantum effect devices

Abstract

A simple numerical method is presented to include the phenomenon of a finite quantum well capture time in the numerical simulation of quantum effect devices. If the time taken to leave the quantum well (through tunnelling) is sufficiently short the electron states in the quantum well will remain relatively unoccupied due to the finite scattering time from the three-dimensional continuum into the two-dimensional states. A numerical formulation is presented which models this phenomenon by using an effective Fermi function for the occupancy of the two-dimensional states, enabling the method to be used in conjunction with general purpose device simulators. The method is applied to a simple tunnel barrier to show the generality of the model and a method is proposed to measure the capture time of quantum wells via observing the output energy spectrum.