Electron microscopy characterization of GaN films grown by molecular‐beam epitaxy on sapphire and SiC
作者:
Zuzanna Liliental‐Weber,
Hyunchul Sohn,
Nathan Newman,
Jack Washburn,
期刊:
Journal of Vacuum Science&Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena
(AIP Available online 1995)
卷期:
Volume 13,
issue 4
页码: 1578-1581
ISSN:1071-1023
年代: 1995
DOI:10.1116/1.588190
出版商: American Vacuum Society
关键词: FILMS;GALLIUM NITRIDES;MOLECULAR BEAM EPITAXY;ELECTRON MICROSCOPY;SUBSTRATES;SILICON CARBIDES;SAPPHIRE;COMPARATIVE EVALUATIONS;CRYSTAL DEFECTS;TWINNING;GaN
数据来源: AIP
摘要:
Transmission electron microscopy was used for the characterization of GaN epitaxial layers grown by molecular‐beam epitaxy on two different substrates: sapphire (Al2O3) and 6H‐SiC. GaN layers grown on both substrates crystallize with the wurtzite structure. Despite the very different lattice mismatch associated with their two substrates, similar types of defects were formed in the GaN layer; only their density differed. In addition to small‐angle subgrain boundaries two other types of defects were seen in cross‐sectioned samples: defects parallel to the growth surface and microtwins with a width of about 8–10 nm perpendicular to the growth surface. The parallel defects were identified as stacking faults leading to a local fcc atom arrangement in the layer and are believed to be growth defects. The density of these faults decreased with layer thickness. However, the density of the vertical microtwins remained constant through the layer. Slight local lattice twists between the microtwins and surrounding areas or differences of stoichiometry are suggested as an explanation for the observed contrast of the high‐resolution images.
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