Resonant interaction of electrons with a high frequency electric field in two-barrier structures

Abstract

The frequency dependences of the small-signal dynamic conductivity of symmetric and nonsymmetric two-barrier heterostructures are calculated in a one-electron approximation. Special attention is focused on the case of electron tunnelling through the upper minibands. In the approximation of high-barrier power (width), an analytic expression is obtained for the dynamic conductivity of a two-barrier resonance-tunnel structure that agrees with a rigorous calculation. It is shown that (a) the dynamic conductivity increases as the fourth power of the barrier width, (b) quantum transitions with an even change in the level number are forbidden, and (c) the dynamic conductivity is inversely proportional to the cube of the frequency if the separation between the levels varies with frequency in a way such that the resonance condition is always satisfied. The maximum possible intensity of the radiating transitions of twobarrier heterostructures are calculated as a function of the quantum numbers of the working levels under conditions such that the supply current density and the characteristic time for breakup of the coherence by phonon scattering are constant. It is shown that the intensity increases significantly if, for example, the fourth level of the structure, rather than the ground state, is used as the working level.