  We show theoretically that nearly indistinguishable photons can be generated
with non-identical semiconductor-based sources. The use of virtual Raman
transitions and the optimization of the external driving fields increases the
tolerance to spectral inhomogeneity to the meV energy range. A trade-off
emerges between photon indistinguishability and efficiency in the
photon-generation process. Linear (quadratic) dependence of the coincidence
probability within the Hong-Ou-Mandel setup is found with respect to the
dephasing (relaxation) rate in the semiconductor sources.
