We report a LTPL (Low Temperature PhotoLuminescence) investigation of nominally undoped 4H-SiC epitaxial layers grown on (0001) 4H-SiC substrates. From room temperature Raman spectra, we find evidence of 3C micro-crystalline inclusions (MCIs). From LTPL spectra collected at various distance from the MCIs we find a coexistence of various defects, which behave like quantum wells (QWs) with various effective thickness. Using a 2-dimensional QW approximation we deduce the extent of the perturbation associated with the different defects.