DYNAMICS OF DOUBLE-BARRIER RESONANT-TUNNELING STRUCTURES

A time-dependent Schrodinger equation is solved numerically for a doub le-barrier, quantum-well resonant tunnelling structure (RTS), such as modelling a semiconductor heterostructure, by the fast Fourier transfo rm method. Results are shown for a resonance tunnelling structure with barriers doped by a negative delta-function potential (delta-potentia l) which broadens the widths of the resonances and in turn decrease th e 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 del ta-potentials are replaced by equivalent barriers of different heights and widths. It is found that for a certain strength of the delta-pote ntial or parametric value of a barrier with an equivalent effect in th e RTS, there are three resonance states very close together. The squar es of the wave functions trapped in the well region for the states osc illate in lime for a broad wave packet in k-space, whereas the wave fu nction trapped in the whole structure decays exponentially. The oscill ating part resembles quantum beats.