Effect of temperature on Raman scattering in hexagonal ZnMgO for optoelectronic applications

We have carried out a detailed investigation of temperature-dependent micro-Raman scattering on hexagonal ZnMgO films with different Mg compositions (0–0.323). The phonon frequencies downshift and linewidths broadening of A 1 [longitudinal optical (LO)] and E 1 (LO) modes can be well explained by a model involving the contributions of thermal expansion, lattice-mismatch-induced strain, and anharmonic phonon processes. We have elucidated the variation with Mg composition of the contribution of the three- and four-phonon processes in the anharmonic effect. The present work establishes an experimental base for the micro-Raman technique to monitor the local temperature during the ZnMgO-based device operation with a submicrometer spatial resolution.