Recent Results From Epitaxial Growth on Step Free 4H-SiC Mesas
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0911-B08-03
Recent Results From Epitaxial Growth on Step Free 4H-SiC Mesas Philip G. Neudeck1, Andrew J. Trunek2, David J. Spry2, J. Anthony Powell3, Hui Du4, Marek Skowronski4, Nabil D. Bassim5, Michael A. Mastro5, Mark E. Twigg5, Ronald T. Holm5, Richard L. Henry5, and Charles R. Eddy, Jr. 5 1 Sensors and Electronics Branch, NASA Glenn Research Center, 21000 Brookpark Road, M.S. 77-1, Cleveland, OH, 44135 2 OAI, NASA Glenn Research Center, 21000 Brookpark Road, M.S. 77-1, Cleveland, OH, 44135 3 Sest, Inc., NASA Glenn, 21000 Brookpark Road, M.S. 77-1, Cleveland, OH, 44135 4 Dept. of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA, 15213 5 Electronics Science and Technology Div., Naval Research Laboratory, Washington, DC, 20375 ABSTRACT This paper updates recent progress made in growth, characterization, and understanding of high quality homoepitaxial and heteroepitaxial films grown on step-free 4H-SiC mesas. First, we report initial achievement of step-free 4H-SiC surfaces with carbon-face surface polarity. Next, we will describe further observations of how step-free 4H-SiC thin lateral cantilever evolution is significantly impacted by crystal faceting behavior that imposes non-uniform film thickness on cantilever undersides. Finally, recent investigations of in-plane lattice constant mismatch strain relief mechanisms observed for heteroepitaxial growth of 3C-SiC as well as 2H-AlN/GaN heterofilms on step-free 4H-SiC mesas will be reviewed. In both cases, the complete elimination of atomic heterointerface steps on the mesa structure enables uniquely well-ordered misfit dislocation arrays to form near the heterointerfaces with remarkable lack of dislocations threading vertically into the heteroepilayers. In the case of 3C-SiC heterofilms, it has been proposed that dislocation half-loops nucleate at mesa edges and glide laterally along the step-free 3C/4H interfaces. In contrast, 3C-SiC and 2H-AlN/GaN heterofilms grown on 4H-SiC mesas with steps exhibit highly disordered interface misfit dislocation structure coupled with 100X greater density of dislocations threading through the thickness of the heteroepilayers. These results indicate that the presence of steps at the heteroepitaxial interface (i.e., on the initial heteroepitaxial nucleation surface) plays a highly important role in the defect structure, quality, and relaxation mechanisms of single-crystal heteroepitaxial films.
INTRODUCTION The ability to produce arrays of device sized (up to 0.4 mm x 0.4 mm) 4H-SiC mesas with silicon-face (0001) top surfaces entirely free of atomic scale steps [1] has enabled realization of unique and improved wide bandgap epitaxial films. For example, when heteroepitaxial films of 3C-SiC or AlN/GaN are properly grown on top of such step-free 4H mesa surfaces, 100-fold reductions in heterofilm dislocation density have been achieved compared with growth on conventional surfaces with steps [2-4]. Furthermore, 4H-SiC thin lateral cantilevers entirely free of dislocations have also been realized [5-7]. D
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