ABSTRACTRaman scattering measurements were carried out on a bulk, single crystal of wurtzite ZnO over a temperature range from 80 to 760 K and the temperature-dependent shift and broadening of the E2high and A1(LO) modes was analyzed. The E2high mode exhibits a visibly asymmetric line shape that can be related to the interaction with the continuum of acoustic two-phonon density of states. A Fermi resonance model was used to describe the E2high temperature dependence. On the other hand, the anharmonic shift and broadening of the A1(LO) mode are adequately accounted for by a decay model with a dominating Ridley channel involving TO and LA modes. Phonon lifetimes of ∼0.9 and 0.5 ps are found for the E2high and A1(LO) modes, respectively, which corroborates that anharmonic decay involves in both cases a three-phonon process. The A1(LO)lifetime is one order of magnitude lower than that of GaN, which suggests that hot phonon effects should be expected to play a less relevant role in carrier relaxation in ZnO as compared with GaN.
Photoluminescence and Lifetime Measurement for the Excitation and Temperature Dependence of Carrier Relaxation in III-V Semiconductors