Analysis of Defects in Physical Vapor Transport Grown 4H-SiC Substrates and Chemical Vapor Deposition Grown Homo-Epitaxial Layers Using Synchrotron X-ray Topography
Synchrotron White Beam X-ray Topography studies are presented of dislocation behavior and interactions in 4H-SiC wafers grown using Physical Vapor Transport under specially designed low stress conditions. Such low stress growth conditions have enabled reductions of dislocation density by two or three orders of magnitude compared to the lowest previously reported levels.
For example, detailed analysis of transmission geometry topographs recorded from wafers ranging in thickness from four hundred to seven hundred microns demonstrates extremely low defect basal plane dislocation (BPD) densities of just a few hundred per square centimeter on average. Lowering of dislocation densities to such levels provides a unique opportunity to discern the details of dislocation configurations and interactions which were previously precluded due to complications of image overlap at higher densities.
In this paper, detailed topography analysis will be presented of the deflection onto the basal plane of c-axis threading dislocations of Burgers vector 1/3<11-20>, 1/3<11-23>, and  which produces new types of dislocation sources as well as some novel faulted defect configurations. The transfer of such substrate defect configurations into subsequently grown homo-epitaxial layers will be discussed. Processes of stress relaxation and generation of new defects during epitaxy will also be presented.
Dr. Michael Dudley is Professor and Chair of the Materials Science and Engineering Department at Stony Brook University. He has been involved in the crystal growth and characterization of technologically important single crystals for more than 30 years. He has edited 7 books, published more than 350 refereed articles and a further 15 chapters in books and his work has been cited more than 2700 times. He has also chaired or co-chaired some 20 conferences in the area of crystal growth, materials characterization and device manufacture and testing. Dudley and co-workers have applied X-ray topography techniques to analyze defects and generalized strain fields in single crystals in general, with particular emphasis on semiconductor, optoelectronic, and optical crystals, especially SiC, GaN, AlN, InP CdZnTe, HgCdTe, ZnO, B12As2, ZnSe as well as proteins and other related materials.
Establishing the relationship between crystal growth conditions and resulting defect distributions is a particular thrust area of interest, as is the correlation between electronic/optoelectronic device performance and defect distribution. Through collaboration with research groups both in academia and industry, several crystal growth development programs have been carried out or are in progress that extensively use the Stony Brook Synchrotron Topography Station at beamline X19C, NSLS. These efforts are anticipated to continue at NSLS-II and at the APS. Current projects include the development of low defect density SiC crystals for power electronics and AlN and sapphire crystals for LED applications.