  We present a quantum theoretical analysis of the electroluminescence from an
intersubband transition of a quantum well structure embedded in a planar
microcavity. By using a cluster factorization method, we have derived a closed
set of dynamical equations for the quantum well carrier and cavity photon
occupation numbers, the correlation between the cavity field and the
intersubband polarization, as well as polarization-polarization contributions.
In order to model the electrical excitation, we have considered electron
population tunneling from an injector and into an extractor contact. The
tunneling rates have been obtained by considering the bare electronic states in
the quantum well and the limit of validity of this approximation (broad-band
injection) are discussed in detail. We apply the present quantum model to
provide a comprehensive description of the electronic transport and optical
properties of an intersubband microcavity light emitting diode, accounting for
non-radiative carrier relaxation and Pauli blocking. We study the enhancement
of the electroluminescence quantum efficiency passing from the weak to the
strong polariton coupling regime.
