ISSN:
1662-9752
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Through the use of specially-prepared on-axis SiC substrates with patterned mesa topscompletely free of atomic-scale surface steps, we have previously reported the growth of highqualityGaN heteroepitaxial films with greatly reduced threading dislocation densities on the orderof 107/cm2. In these films, we reported a defect substructure in which lateral a-type dislocations arepresent in the nucleation layer but do not bow into threading dislocations during the subsequentGaN growth. This study focuses further on the role of SiC substrate surface steps in the generationof misfit, a-type, and threading dislocations at the heteroepitaxial interface. By using weak-beamimaging (both to eliminate Moiré effects and to observe narrow dislocation images) from plan-viewtransmission electron microscopy (TEM), we identify dislocations generated on stepped andunstepped mesas and compare their geometries. We observe that misfit dislocations nucleated on anunstepped SiC mesa are confined to one set of a-type Burgers vectors of the form g=1/3 [2110]_ _,straight and well-ordered so that they are less likely to interact with each other. On the other hand,misfit dislocation structures on a stepped SiC mesa surface are not nearly as well-ordered, havingbowed structure with threading dislocations that appear to nucleate at SiC surface steps
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/14/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.527-529.1509.pdf
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