We consider semiconductor heterostructures in nanometric quantum wells, which as a consequence of the growth process display at the rugged interfaces fractal characteristics, and largely influence optical and transport properties of the carriers system. The photoluminescence and excited photoluminescence spectra in such fractal conditions are theoretically analyzed, obtaining good agreement with the experimental results. The Stokes shift and linewidth are strongly dependent on the nonequilibrium thermomechanical-statistical state of the system. The Stokes shift has its origin in the presence of a gain region in the absorption spectrum, only present when the carriers system is in a statistical degenerate state.