a Key Laboratory of Instrumentation Science & Dynamic Measurement (North University of China), Ministry of Education; bNational Key Laboratory for Electronic Measurement Technology North University of China, Taiyuan 030051, China; c The 13th research institute of CETC, Shijiazhuang 050051, China
Abstract Hexagonal GaN epilayer grown on sapphire substrate by metal organic chemical vapour deposition (MOCVD) is studied using Raman scattering and photoluminescence in a temperature range from 100 K to 873 K. The model of strain (stress) induced by the different lattice parameters and thermal coefficients of epilayer and substrate as a function of temperature is set up. The frequency and the linewidth of $E_2^{\rm high}$ mode in a GaN layer are modelled by a theory with considering the thermal expansion of the lattice, a symmetric decay of the optical phonons, and the strain (stress) in the layer. The temperature-dependent energy shift of free exciton A is determined by using Varshni empirical relation, and the effect of strain (stress) is also investigated. We find that the strain in the film leads to a decreasing shift of the phonon frequency and an about 10meV-increasing shift of the energy in a temperature range from 100 K to 823 K.
Received: 15 October 2007
Revised: 26 December 2007
Accepted manuscript online:
Fund: Project supported by the National
Natural Science Foundation of China (Grant Nos 50405025 and
50535030) and Program for New Century
Excellent Talents in University, China.
Cite this article:
Xu Hong-Yan(徐宏妍), Jian Ao-Qun(菅傲群), Xue Chen-Yang(薛晨阳), Chen Yang(陈阳), Zhang Bin-Zhen(张斌珍), Zhang Wen-Dong(张文栋), Zhang Zhi-Guo(张志国), and Feng Zhen(冯震) Temperature dependence of biaxial strain and its influence on phonon and band gap of GaN thin film 2008 Chin. Phys. B 17 2245
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