Study on the relationships between Raman shifts and temperature range for a -plane GaN using temperature-dependent Raman scattering

• Published in: Chinese physics B Vol. 22; no. 2; pp. 28101 - 1-028101-5
• Main Authors: Wang, Dang-Hui, Xu, Sheng-Rui, Hao, Yue, Zhang, Jin-Cheng, Xu, Tian-Han, Lin, Zhi-Yu, Zhou, Hao, Xue, Xiao-Yong
• Format: Journal Article
• Language: English
• Published: 01.02.2013
• Subjects: Anharmonicity; Crystals; Gallium nitrides; Insertion; Mathematical analysis; Phonons; Raman scattering; Superlattices
• ISSN: 1674-1056; 1741-4199
• DOI: 10.1088/1674-1056/22/2/028101

In this paper, Raman shifts of a-plane GaN layers grown on r-plane sapphire substrates by low-pressure metal-organic chemical vapor deposition (LPMOCVD) are investigated. We compare the crystal qualities and study the relationships between Raman shift and temperature for conventional a-plane GaN epilayer and insertion AlN/AlGaN superlattice layers for a-plane GaN epilayer using temperature-dependent Raman scattering in a temperature range from 83 K to 503 K. The temperature-dependences of GaN phonon modes (A sub(1) (TO), E sub(2) (high), and E sub(1) (TO)) and the linewidths of E sub(2) (high) phonon peak are studied. The results indicate that there exist two mechanisms between phonon peaks in the whole temperature range, and the relationship can be fitted to the pseudo-Voigt function. From analytic results we find a critical temperature existing in the relationship, which can characterize the anharmonic effects of a-plane GaN in different temperature ranges. In the range of higher temperature, the relationship exhibits an approximately linear behavior, which is consistent with the analyzed results theoretically.