Anisotropic strain relaxation and abnormal zigzag shape planar defects in nonpolar a-GaN grown by metalorganic chemical vapor deposition

• Published in: Journal of crystal growth 2010-12, Vol.313 (1), p.8-11
• Main Authors: Hyun Kong, Bo, Koun Cho, Hyung, Man Song, Keun, Ho Yoon, Dea
• Format: Article
• Language: English
• Subjects: A1. Crystal structure; A1. Planar defects; A3. Metalorganic chemical vapor deposition; Anisotropy; B1. Nitrides; B2. Semiconducting III–V materials; Chemical vapor deposition (including plasma-enhanced cvd, mocvd, etc.); Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Crystal defects; Crystal growth; Defects and impurities in crystals; microstructure; Deviation; Dislocations; Exact sciences and technology; Linear defects: dislocations, disclinations; Materials science; Metalorganic chemical vapor deposition; Methods of deposition of films and coatings; film growth and epitaxy; Physics; Residual stress; Stacking faults; Stacking faults and other planar or extended defects; Stress relaxation; Structure of solids and liquids; crystallography; Structure of specific crystalline solids
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2010.09.084

The correlation between bi-axial in-plane stress relaxation and formation mechanism of the abnormal zigzag shape prismatic stacking faults (PSFs) observed in a-GaN epilayers grown by metalorganic chemical vapor deposition was investigated using transmission electron microscopy. In a-GaN epilayers on r-plane sapphire substrates showing an anisotropic lattice mismatch, the misfit strain along the [0 0 0 1] GaN direction was mostly relaxed by the formation of basal stacking faults. On the other hand, the [1¯ 1 0 0] GaN direction with a larger misfit had an in-plane residual stress of ∼3% after the formation of the zigzag shaped PSFs and misfit dislocations. The resultant higher residual stress induced dislocation near the zigzag shaped PSFs junction and ultimately led to abnormal deviation in the junction angle of the zigzag shaped PSFs.