<p>The surface morphology and atomic structure of nitrogen doped, n-type 6H-SiC(0001)Si wafers before and after various surface preparation techniques were investigated. As-received wafers were exposed to in-situ cleaning with or without excess silicon to obtain either a (rt3 x rt3)R30° or a (3 x 3) reconstructed surface. The resulting surfaces were characterized using reflection high-energy electron diffraction, photo-electron emission microscopy, and atomic force microscopy. An atomically clean, reconstructed surface was obtained via thermal annealing at 950ºC. Cleaning with excess silicon resulted in the formation of silicon islands on the surface. The surface morphology of hydrogen etched wafers depended upon their doping concentrations. Wafers with doping concentrations of greater than or equal 2.5 x 10E18 and less than 7 x 10E17 (ND-NA)/cm3 were investigated with the former exhibiting more surface features. The microstructure of all the samples showed regions with full and half unit cell high steps. An atomically clean, ordered, stepped surface was achieved via annealing at 1030 degrees Celcius. Chemical vapor cleaning resulted in the formation of silicon islands. The initial growth of AlN and GaN thin films on the cleaned, hydrogen etched 6H-SiC(0001) substrates were investigated using PEEM and AFM. The AlN films nucleated immediately and coalesced, except in the areas of the substrate surface which contained half unit cell height steps where pits were observed. The GaN films grown at 800ºC for 2.5 minutes exhibited nucleation and three-dimensional growth along the steps. The GaN films deposited at 700° C for 2 minutes grew three-dimensionally with coalescence of the film dependent upon the step structure. Almost complete coalescence occurred in regions with unit cell high steps and incomplete coalesce occurred in regions with half unit cell height steps. Films of AlN grown for 30 minutes via GSMBE on hydrogen etched surfaces exhibited two-dimensional growth and had an RMS roughness value of 4 Å. Films grown at 1000 ° C exhibited an SK growth mode and had rocking curve FWHM of 150-200 arcsecs. MOCVD grown films on hydrogen etched wafers had an RMS roughness value of 4 Å and a XRD rocking curve FWHM of approximately 260 acrsecs. <P>
| Identifer | oai:union.ndltd.org:NCSU/oai:NCSU:etd-20001013-161053 |
| Date | 16 October 2000 |
| Creators | Hartman, Jeffrey David |
| Contributors | Robert F. Davis, Robert J. Nemanich, Zlatko Sitar, Salah M. Bedair |
| Publisher | NCSU |
| Source Sets | North Carolina State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://www.lib.ncsu.edu/theses/available/etd-20001013-161053 |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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