Synchrotron white beam topography characterization of physical vapor transport grown AlN and ammonothermal GaN

• Published in: Journal of crystal growth 2002-12, Vol.246 (3), p.271-280
• Main Authors: Raghothamachar, Balaji, Vetter, William M., Dudley, Michael, Dalmau, Rafael, Schlesser, Raoul, Sitar, Zlatko, Michaels, Emily, Kolis, Joseph W.
• Format: Article
• Language: English
• Subjects: A1. Defects; A1. X-ray topography; A2. Growth from vapor; A2. Single crystal growth; B1. Aluminum nitride; B1. Gallium nitride; Condensed matter: structure, mechanical and thermal properties; Defects and impurities in crystals; microstructure; Exact sciences and technology; Physics; Structure of solids and liquids; crystallography
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/S0022-0248(02)01751-7

Structural defects in AlN single crystals grown by the sublimation method and GaN single crystals grown by the ammonothermal method are characterized by synchrotron white-beam X-ray topography in conjunction with optical microscopy. AlN platelets are either of (1 1 2 ̄ 0) or (0 0 0 1) type depending on the growth conditions. Dislocation densities of the order of 10 3 cm −2 or lower are observed in some crystals. X-ray topographs reveal the presence of growth sector boundaries, inclusions, and growth dislocations that indicate slight impurity contamination. The 2H crystal structure of GaN single crystals obtained by the ammonothermal method was verified by Laue X-ray pattern analysis. GaN crystals grown are of the order of 1 mm in size and are either (0 0 0 1) platelets or [0 0 0 1] prismatic needles. Generally, prismatic needles are characterized by lower degree of mosaicity than (0 0 0 1) platelets.