Observation of symmetrically decay of A1(longitudinal optical) mode in free-standing GaN bulk single crystal from Li3N flux method

Abstract

We report Raman analysis of A1(LO) (longitudinal optical) and E2(high) phonon lifetimes in a bulk GaN single crystal and their temperature dependence from 77 K to 770 K. Both the A1(LO) and E2(high) phonons in GaN were observed decaying primarily into two phonons of equal energy [Klemens model, P. G. Klemens, Phys. Rev. 148, 845 (1966)]. This is a rare example of a high-quality free-standing GaN bulk single crystal displaying abnormal A1(LO) phonon decay. These results will have significant impact on designing and understanding of GaN-based high-speed, high-power electric devices.