  We theoretically investigate polarization-entangled photon generation by
using a semiconductor quantum dot embedded in a microcavity. The entangled
states can be produced by the application of two cross-circularly polarized
laser fields. The quantum dot nanostructure is considered as a four-level
system (ground, two excitons and bi-exciton states) and the theoretical study
relies on the dressed states scheme. The quantum correlations, reported in
terms of the entanglement of formation, are extensively studied for several
values of the important parameters of the quantum dot system as the bi-exciton
binding energy, {the decoherence times of the characteristic transitions, the
quality factor of the cavity} and the intensities of the applied fields.
