The emphasis in this project was on in situ observation of defect nucleation processes by carrying out CVD homoepitaxial growth of 6Hand 4H-SiC growth in a chamber specially designed to enable synchrotron white beam X-ray topographic (SWBXT) in situ observation of the growing crystal, both bulk and surface regions. In addition a significant amount of ex situ topographic work was carried out on wafers sliced from boules grown in situ in the X-ray beam and boules not grown in situ in the X-ray

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... m. The growth system was set up using commercially procured gas flow controls and scrubber units, and integrating them with a modified in-house designed growth chamber that has options for in situ X-ray topographic study. The CVD system uses silicon tetrachloride (SiC1 4 ). silane (Sill 4 ), propane (C 3 H 8 ), hydrogen (H 2 ) and argon (Ar) gases. The hot-zone design and growth conditions were optimized by using numerical modeling as well as thermodynamic modeling. Detailed numerical modeling showed how the temperature field contours get shifted towards the exit end of the hot-zone depending on the associated thermal capacity of the gases at different flow rates. Detailed experiments were performed in both the kinetically and thermodynamically controlled regions, achieved by altering the growth parameters, and the results compared with our equilibrium model. This enabled it to be determined that kinetically controlled CVD growth is more effective, and that 6H-SiC homo-epitaxial layers grown at about 1500'C in this condition resulted in high quality films in terms of surface morphology and lower basal plane dislocation density. 20081002144 REPORT DOCUMENTATION PAGE Form Approved R R DOMB No. 0704-0188 The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.