Calculation of Excitonic Transitions in ZnO/MgZnO Quantum-WellHeterostructures

We calculate the excitonic transition energies and exciton binding energies in ZnO/Mg_xZn_1-xO quantum-well heterostructures with Mg composition x varied from 0.08 to 0.36. The effect of the exciton-phonon interaction on the exciton binding energies is taken into account in the model. For the ZnO/Mg_0.12Zn_0.88O quantum-well structure, we compare the calculated result with the available experimental data at 5 K, and a good agreement is achieved. The excitonic transition energies at room temperature in ZnO/Mg_xZn_1-xO quantum-well heterostructures are also calculated. The results show that when the well width exceeds 50Å, the quantum size effect is neglectable and the excitonic transition energies in ZnO/Mg_xZn_1-xO (with x varied from 0.08 to 0.36) quantum-well heterostructures are close to the value of bulk ZnO. The maximum exciton binding energy as large as 121.1 meV is obtained for the well width of 12.5Å in the ZnO/Mg_0.36Zn_0.64O quantum-well heterostructures.