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Microstructure and strain analysis of GaN epitaxial films using in-plane grazing incidence x-ray diffraction
Guo Xi (郭希), Wang Yu-Tian (王玉田), Zhao De-Gang (赵德刚), Jiang De-Sheng (江德生), Zhu Jian-Jun (朱建军), Liu Zong-Shun (刘宗顺), Wang Hui (王辉), Zhang Shu-Ming (张书明), Qiu Yong-Xin (邱永鑫), Xu Ke (徐科), Yang Hui (杨辉)
Chin. Phys. B, 2010, 19 (7):
076804.
DOI: 10.1088/1674-1056/19/7/076804
This paper investigates the major structural parameters, such as crystal quality and strain state of (001)-oriented GaN thin films grown on sapphire substrates by metalorganic chemical vapour deposition, using an in-plane grazing incidence x-ray diffraction technique. The results are analysed and compared with a complementary out-of-plane x-ray diffraction technique. The twist of the GaN mosaic structure is determined through the direct grazing incidence measurement of (100) reflection which agrees well with the result obtained by extrapolation method. The method for directly determining the in-plane lattice parameters of the GaN layers is also presented. Combined with the biaxial strain model, it derives the lattice parameters corresponding to fully relaxed GaN films. The GaN epilayers show an increasing residual compressive stress with increasing layer thickness when the two dimensional growth stage is established, reaching to a maximum level of —0.89 GPa.
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