Reducing exciton–longitudinal optical phonon coupling with increasing Mg incorporation in MgZnO powders

The coupling between exciton and longitudinal optical (LO) phonon was investigated in the use of temperature-dependent photoluminescence from MgxZn1−xO powders prepared by a sol-gel method in the range of 0≤x≤0.05. The exciton binding energy increases to 73 meV for 5 at. % Mg incorporated powders. The strength of exciton–LO phonon coupling was deduced from the energy shift of exciton emission with temperature variation. The increase of the exciton binding energy results from a decrease of the exciton Bohr radius that is responsible for reducing the coupling strength of exciton–LO phonon as increasing Mg content.