  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, sub-peak voltages, second resonance
voltages), and as a function of temperature, explaining experimental results
and predicting interesting new results.
