Raman scattering behaviors of GaN single crystal grown by a Na flux method

Bulk GaN single crystals above 4mm in size were grown by a Na flux method. Micro-Raman scattering from bulk GaN crystals was performed over the temperature range from 80 K to 300 K. The results obtained reveal that Raman phonon frequency decreases with increasing temperature. This temperature dependence of optical phonons is well described by an empirical relationship that has proved to be effective for other semiconductors. Small 667 cm(-1) peaks appeared systematically on every piece of bulk GaN. We suggest that lattice-disorder-induced modes are mainly responsible for the 667 cm(-1) peaks associated with the presence of Fe and Cr ions in the GaN crystals grown by the Na flux method.