Temperature response and anharmonicity of the optical phonons in GaN nanowires

• Published in: Journal of applied physics 2005-07, Vol.98 (2), p.026106-026106-3
• Main Authors: Chen, Xiang-Bai, Huso, Jesse, Morrison, John L., Bergman, Leah, Purdy, Andrew P.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.1968425

Anharmonic decay mechanisms of longitudinal-optical (LO) phonons in wurtzite-structured GaN nanowires were studied by temperature-dependent Raman scattering at the temperature range of 77 - 900 K . It was found that with increasing temperature, the LO-phonon linewidth increases and the Raman frequency decreases. The LO-linewidth behavior was analyzed in terms of the anharmonic effect of two- and three-phonon decay mechanisms. We found that for a temperature regime up to the Debye temperature ∼ 830 K , the two-phonon decay contributes the major increase to the linewidth and the three-phonon decay mechanism is marginal. The Raman frequency was studied in terms of the anharmonic decay and the thermal expansion of the lattice. Our analysis indicates that the anharmonic interaction due to the two-phonon decay as well as the thermal-expansion contribution both need to be taken into consideration. Additionally, in analyzing the linewidth of the nanowires, a temperature-independent term, which usually is not included when analyzing bulk material, had to be considered. The temperature-independent term reflects the inhomogeneous nature of the crystallite ensemble.