Piezoelectric and spontaneous polarization effects on exciton binding energy and light emission properties of wurtzite ZnO/MgO quantum dots

Exciton binding energies and light emission characteristics for wurtzite (WZ) cubic ZnO/MgO quantum dots (QDs) are investigated by considering piezoelectric (PZ) and spontaneous (SP) polarizations. These results are compared with those for the flat-band without PZ and SP polarizations. The exciton binding energies for the case with PZ and SP polarizations appears to be smaller than those for the flat-band model. In particular, the spontaneous emission coefficients are shown to be reduced significantly by the built-in field because the existence of the built-in field results in the decrease in the overlap between the electron and hole wave functions. These results show that the consideration of PZ and SP polarizations is very important in predicting optical properties of ZnO-based QD devices.