Figure 32: Dependence of the photoluminescence energy (left scale) and decay time (right scale) taken at the maximum of the QW luminescence of PLD grown QW samples (Figure 31), on the thickness of the ZnO quantum wells. Closed symbols give data obtained in [76] with remarkable QCSE. Crosses symbolize data from PLD grown samples without remarkable QCSE [77]. The black dotted line shows the free exciton transition energy in bulk ZnO. Solid lines give the expected dependence from the variational calculations with the presence of an electrical polarization mismatch. The dashed red line gives the transition energy as from variational calculations without a mismatch in the electrical polarization.