Effect of defects on strain state in nonpolar a-plane GaN

• Published in: Journal of crystal growth Vol. 343; no. 1; pp. 122 - 126
• Main Authors: Liu, Z.Y., Xu, S.R., Zhang, J.C., Xue, J.S., Xue, X.Y., Niu, M.T., Hao, Y.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.03.2012
• Subjects: A1. Defects; A1. High resolution X-ray diffraction; Anisotropy; B1. Nitrides; B2. Semiconducting III–V materials; Compressive properties; Crystal defects; Density; Gallium nitrides; Sapphire; Stacking faults; Strain; B1. Nitrides; B2. Semiconducting III–V materials; A1. High resolution X-ray diffraction; A1. Defects
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2012.01.001

We have investigated the influence of basal stacking fault (BSF) and impurity related defect on the strain state of a-plane GaN epilayers. Four a-plane GaN epilayers were grown on r-plane sapphire using different growth strategies by metalorganic chemical vapor deposition. It is found that with a growing number of stacking fault, both the anisotropic in-plane strain and compressive out-plane strain along c-axis are relieved. Epitaxial lateral overgrowth with a TiN interlayer is an effective way to relieve in-plane strain and reduce BSF density. The extrapolated lattice parameters free of biaxial strain increase with the normalized yellow luminescence intensity. Hydrostatic strain induced by impurity-related defects is the possible cause of this phenomenon. ► Anisotropic strain in a-plane GaN can be relaxed with increasing number of BSF. ► Impurity related defect causes hydrostatic strain. ► Hydrostatic strain is secondary to biaxial one. ► Higher the impurity level is, the larger lattice parameter presents.