Ultrathin wide band gap II-VI quantum wells (QW's) feature a large inhomogeneous broadening of exciton transitions in the optical absorption and photoluminescence (PL) spectra. When the photon energy of the excitation laser approaches, or lies within the broadened PL band, a series of additional sharp peaks appear at low energy. The laser induced linear polarisation of the sharp peaks enables the clear demonstration of evenly spaced phonon-assisted transitions. The relative intensity of the phonon-assisted transitions and the mean phonon energy depend strongly on the photon energy of the exciting light. A new model of phonon-assisted relaxation between classically localized states explains these results well.
- quantum wells
- optical absorption