DYNAMICS OF DOUBLE-BARRIER RESONANT-TUNNELING STRUCTURES

A time-dependent Schrodinger equation is solved numerically for a double-barrier, quantum-well resonant tunnelling structure (RTS), such as modelling a semiconductor heterostructure, by the fast Fourier transform method. Results are shown for a resonance tunnelling structure with barriers doped by a negative delta-function potential (delta-potential) which broadens the widths of the resonances and in turn decrease the electron dwell times. The strength of the delta-function can be such that it may form bound states in the barrier regions, but the states bound to the delta-potential are very shallow. For this study, the delta-potentials are replaced by equivalent barriers of different heights and widths. It is found that for a certain strength of the delta-potential or parametric value of a barrier with an equivalent effect in the RTS, there are three resonance states very close together. The squares of the wave functions trapped in the well region for the states oscillate in lime for a broad wave packet in k-space, whereas the wave function trapped in the whole structure decays exponentially. The oscillating part resembles quantum beats.