Resonant Raman scattering in ZnO

The resonance of the Raman scattering by $E_2, A_{1T}, E_{1L}$, and $E_{1T}$ phonons, and several second-order features, has been studied for ZnO for photon energies between 1.6 and 3 eV. The results are interpreted with a dielectric theory based on the first and second derivatives of the dielectric constant. By combining our results with absolute scattering cross sections previously determined by Arguello et al. at 2.41 eV absolute values of the deformation potentials of the band edge can be determined. The difference in strength between the longitudinal and the transverse modes provides the signs of these deformation potentials. The antiresonance around 1.6 eV suggested by the earlier work of Callender et al. and attributed to a cancellation of the deformation potential and electro-optical contributions to the Raman tensor is confirmed. The deformation potentials of the $A_1$ phonons at the band edge have been obtained from a pseudopotential calculation. While the sign of these deformation potentials agrees with the experimental determination, their magnitudes do not agree. This fact is attributed to difficulties with the pseudopotential of the ${\mathrm{O}}^{2-}$ ion. An estimate of the deformation potentials from the dependence of the band edges on uniaxial stress is also made.