Defect Structures in B12As2 Epitaxial Layers Grown on (0001) 6H-SiC
A detailed analysis of the microstructure in B{sub 12}As{sub 2} epitaxial layers grown by chemical-vapor deposition on (0001) 6H-SiC substrates is presented. Synchrotron white beam x-ray topography enabled macroscopic characterization of the substrate/epilayer ensembles and revealed the presence of a quite homogeneous solid solution of twin and matrix epilayer domains forming a submicron mosaic structure. The basic epitaxial relationship was found to be (0001){sub B{sub 12}As{sub 2}} (1120){sub B{sub 12}As{sub 2}} the norm of (0001){sub 6H-SlC} and the twin relationship comprised by a 180{sup o} (or equivalently 60{sup o}) rotation about (0001){sub B{sub 12}As{sub 2}} in agreement with previous reports. Cross-sectional high resolution transmission electron microscopy revealed the presence of {approx} 200 nm thick disordered transition layer which was shown to be created by the coalescence of a mosaic of translationally and rotationally variant domains nucleated at various types of nucleation sites available on the (0001) 6H-SiC surface. In this transition layer, competition between the growth of the various domains is mediated in part by the energy of the boundaries created between them as they coalesce. Boundaries between translationally variant domains are shown to have unfavorable bonding configurations and hence high-energy. These high-energy boundaries can be eliminated during mutual overgrowth by the generation of a 1/3(0001)B{sub 12}As{sub 2} Frank partial dislocation which effectively eliminates the translational variants. This leads to an overall improvement in film quality beyond thicknesses of {approx} 200nm as the translational variants grow out leaving only the twin variants. (0003) twin boundaries in the regions beyond 200 nm are shown to possess fault vectors such as 1/6(100)B{sub 12}As{sub 2}, which are shown to originate from the mutual shift between the nucleation sites of the respective domains.
- Research Organization:
- Brookhaven National Laboratory (BNL) National Synchrotron Light Source
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- AC02-98CH10886
- OSTI ID:
- 980130
- Report Number(s):
- BNL--93048-2010-JA
- Journal Information:
- Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 12 Vol. 103; ISSN JAPIAU; ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
43 PARTICLE ACCELERATORS
BEAMS
BONDING
COALESCENCE
COMPETITION
DEFECTS
DEPOSITION
DISLOCATIONS
ENERGY
FILMS
GROWTH
LAYERS
MICROSTRUCTURE
NUCLEATION
RESOLUTION
ROTATION
SOLID SOLUTIONS
SUBSTRATES
SYNCHROTRONS
TOPOGRAPHY
TRANSMISSION ELECTRON MICROSCOPY
VECTORS
national synchrotron light source