Shot noise in resonant-tunneling structures

We propose a quantum-mechanical approach to noise in resonant-tunneling structures that can be applied in the whole range of transport regimes, from completely coherent to completely incoherent. In both limiting cases, well-known results which have appeared in the literature are recovered. Shot noise reduction due to both Pauli exclusion and Coulomb repulsion, and their combined effect, are studied as a function of the rate of incoherent processes in the well (which are taken into account by means of a phenomenological relaxation time), and of temperature. Our approach allows the study of noise in a variety of operating conditions (i.e., equilibrium, subpeak voltages, second-resonance voltages), and as a function of temperature, explaining experimental results and predicting interesting results, such as the dependence of noise on filled-emitter states and the prediction of both increasing and decreasing shot noise with increasing temperature, depending on the structure. It also allows the determination of the major contributions to shot-noise suppression by performing noise measurements at the second-resonance voltage.