  We compute the concurrence of the polarization-entangled photon pairs
generated by the biexciton cascade decay of a semiconductor quantum dot. We
show how a cavity-induced increase of the photon rate emission reduces the
detrimental effect of the dot dephasing and of the excitonic fine structure.
However, strong dot-cavity couplings and finite detection efficiencies are
shown to reduce the relevance of the desired cascade decay with respect to that
of competing processes. This affects the merits of the entangled photon-pair
source, beyond what estimated by the quantum-tomography.
