Raman Analysis of Single Crystalline Bulk Aluminum Nitride: Temperature Dependence of the Phonon Frequencies

Abstract

ABSTRACTThe frequencies of the E2(high), A1(LO), A1(TO), E1(TO) and E1(LO) phonons of singlecrystalline bulk AlN were measured using micro-Raman spectroscopy over a temperature range from 10K to 1275K. A modeling of the temperature dependence of the AlN phonon frequencies considering the thermal lattice expansion and two-phonon decay mechanisms gave results in good agreement with the experimental data. At temperatures in excess of ∼300K an approximate linear shift of the phonon frequencies with temperature was found. In this high temperature regime, we determined a frequency shift of the E2(high) phonon of (-2.22 ± 0.02) ×10−2cm−1/K, which is very similar to values reported for bulk GaN. This suggests that similar parameters will be suitable for AlxGa1−xN alloys, commonly used in high-power high-frequency electronic devices. The results provide the basis for non-invasive local temperature monitoring in highpower III-nitride devices using micro-Raman scattering techniques.