Effect of isotopic mass on the photoluminescence spectra of zinc oxide

ZnO is a wurtzite-type semiconductor at ambient conditions whose natural composition consists of almost pure 16O and a mixture of 48.6% 64Zn, 27.9% 66Zn, 4.1% 67Zn, 18.8% 68Zn, and 0.6% 70Zn. In this work, we report a photoluminescence study of different samples of isotopically pure and natural zinc oxide between 15 and 300 K. The isotopic coefficients of the bound exciton energy have been obtained and compared with previous values for the shift of the free A exciton energy. The isotopic coefficients of the bound exciton energy have allowed us to estimate the contribution of the zinc and the oxygen vibrations to the bandgap renormalization by electron–phonon interaction. A two-oscillator model based on the zinc and oxygen renormalization energies has been used to account for the temperature dependence of the bandgap in ZnO.