Phonon-assisted exciton luminescence in a CdSe-ZnSe disordered superlattice

Phonon-assisted luminescence (PAL) of excitons in short-period cubic cadmium selenide-zinc selenide strained layer superlattices is observed when the photon energy of excitation approaches, or lies within, the inhomogeneously broadened exciton luminescence band. Strong induced polarisation of the resulting sharp transitions enables the clear demonstration of several phonon orders. The relative intensity of the PAL and the mean phonon energy depend strongly on the photon energy of the exciting light. The spectroscopic properties of such superlattices is consistent with the localisation of excitons by disorder.