Migration of Dislocations in Strained GaN Heteroepitaxial Layers

• Published in: Physica status solidi. B. Basic research Vol. 234; no. 3; pp. 952 - 955
• Main Authors: Sahonta, S.-L., Baines, M.Q., Cherns, D., Amano, H., Ponce, F.A.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Berlin WILEY-VCH Verlag 01.12.2002; WILEY‐VCH Verlag; Wiley
• Subjects: 68.35.Dv; Composition; defects and impurities; Condensed matter: structure, mechanical and thermal properties; Defects and impurities in crystals; microstructure; Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.); Electron, ion, and scanning probe microscopy; Exact sciences and technology; Physics; Solid surfaces and solid-solid interfaces; Structure of solids and liquids; crystallography; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Transmission, reflection and scanning electron microscopy(including ebic); Inorganic compounds; Epitaxial layers; Misfit dislocations; Gallium nitrides; Binary compounds; Screw dislocations; Experimental study; Dislocation density; Thickness; Stress relaxation; Edge dislocations; Transmission electron microscopy; Aluminium nitrides; Strained layer; Diffusion; III-V semiconductors
• ISSN: 0370-1972; 1521-3951
• DOI: 10.1002/1521-3951(200212)234:3<952::AID-PSSB952>3.0.CO;2-4

Transmission electron microscopy has been used to study the relaxation of misfit strains in GaN/Al0.28Ga0.72N layers grown on (0001) sapphire. It has been observed that threading edge‐type dislocations migrate laterally in the top GaN layer to form misfit dislocations. This leads to reactions with other threading dislocations, to generate either closed loops or more complex nodes, which reduce the total threading dislocation density. The proportion of edge‐type dislocations compared to screw‐type and mixed dislocations is reduced with increasing GaN thickness. It is proposed that the lateral migration of the dislocations is predominantly by a climb rather than a glide mechanism.