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Structural Characterization of Lateral-grown 6H-SiC a/m-plane Seed Crystals by Hot Wall CVD Epitaxy

Published online by Cambridge University Press:  10 June 2014

Ouloide Yannick Goue ,
Balaji Raghothamachar ,
Michael Dudley ,
Andrew J. Trunek ,
Philip G. Neudeck ,
Andrew A. Woodworth  and
David J. Spry
Ouloide Yannick Goue
Affiliation:
Department of Materials Science and Engineering Stony Brook University, Stony Brook, NY 11794-2275, USA
Balaji Raghothamachar
Affiliation:
Department of Materials Science and Engineering Stony Brook University, Stony Brook, NY 11794-2275, USA
Michael Dudley
Affiliation:
Department of Materials Science and Engineering Stony Brook University, Stony Brook, NY 11794-2275, USA
Andrew J. Trunek
Affiliation:
NASA Glenn Research Center, 21000 Brookpark Road, MS 77-1, Cleveland, OH 44135 USA
Philip G. Neudeck
Affiliation:
NASA Glenn Research Center, 21000 Brookpark Road, MS 77-1, Cleveland, OH 44135 USA
Andrew A. Woodworth
Affiliation:
NASA Glenn Research Center, 21000 Brookpark Road, MS 77-1, Cleveland, OH 44135 USA
David J. Spry
Affiliation:
NASA Glenn Research Center, 21000 Brookpark Road, MS 77-1, Cleveland, OH 44135 USA
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Abstract

The performance of commercially available silicon carbide (SiC) power devices is limited due to inherently high density of screw dislocations (SD), which are necessary for maintaining polytype during boule growth and commercially viable growth rates. The NASA Glenn Research Center (GRC) has recently proposed a new bulk growth process based on axial fiber growth (parallel to the c-axis) followed by lateral expansion (perpendicular to the c-axis) for producing multi-faceted m-plane SiC boules that can potentially produce wafers with as few as one SD per wafer. In order to implement this novel growth technique, the lateral homoepitaxial growth expansion of a SiC fiber without introducing a significant number of additional defects is critical. Lateral expansion is being investigated by hot wall chemical vapor deposition (HWCVD) growth of 6H-SiC a/m-plane seed crystals (0.8mm x 0.5mm x 15mm) designed to replicate axially grown SiC single crystal fibers. The post-growth crystals exhibit hexagonal morphology with approximately 1500 μm (1.5 mm) of total lateral expansion. Preliminary analysis by synchrotron white beam x-ray topography (SWBXT) confirms that the growth was homoepitaxial, matching the polytype of the respective underlying region of the seed crystal. Axial and transverse sections from the as-grown crystal samples were characterized in detail by a combination of SWBXT, transmission electron microscopy (TEM) and Raman spectroscopy to map defect types and distribution. X-ray diffraction analysis indicates the seed crystal contained stacking disorders and this appears to have been reproduced in the lateral growth sections. Analysis of the relative intensity for folded transverse acoustic (FTA) and optical (FTO) modes on the Raman spectra indicate the existence of stacking faults (SFs). Further, the density of stacking faults is higher in the seed than in the grown crystal. Bundles of dislocations are observed propagating from the seed in m-axis lateral directions. Contrast extinction analysis of these dislocation lines reveals they are edge type basal plane dislocations that track the growth direction. Polytype phase transition and stacking faults were observed by high-resolution TEM (HRTEM), in agreement with SWBXT and Raman scattering.

Keywords

crystal growthdefectsepitaxy
Type
Articles
Information
MRS Online Proceedings Library (OPL) , Volume 1693: Symposium DD – Silicon Carbide‒Materials, Processing and Devices , 2014 , mrss14-1693-dd01-03
Copyright
Copyright © Materials Research Society 2014 

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