Accession Number : ADA325406
Title : Selected Energy Epitaxial Deposition and Low Energy Electron Microscopy of AlN, GaN and SiC Thin Films.
Descriptive Note : Quarterly rept. 1 Jan-31 Mar 97,
Corporate Author : NORTH CAROLINA STATE UNIV AT RALEIGH
Personal Author(s) : Davis, R. F. ; Lamb, H. H. ; Tsong, I. S. ; Bauer, E. ; Chen, E.
PDF Url : ADA325406
Report Date : MAR 1997
Pagination or Media Count : 33
Abstract : The total energies for various p(2x2) geometries of GaN and AlN(0001) have been computed. Vacancy structures were the most stable configurations for the anion and cation terminated surfaces. In metal rich growth conditions, the calculations favored the adsorption of metal atoms on the cation terminated surface; the adsorption of H stabilized the N terminated surface in the presence of H. Films of AlN and GaN were grown on Si(111) and off axis 6H-SiC(0001) substrates under real time observations in the LEEM. The metals were deposited using evaporative sources; N-atoms were obtained via RF plasma source. Additional homoepitaxial growth of GaN films at typical rate of 20 nm/h was achieved between 600 and 700 C using TEG seeded and NH3 seeded supersonic beams. AFM revealed faceted growth surfaces. XPS indicated the N/Ga ratio at the growth surface approached unity with an increase in the ammonia to TEG flux ratio. TEM analysis of AlN films and subsequently deposited GaN layers grown using evaporated metals and NH3 seeded He supersonic molecular beams showed the latter to be epitaxial with a thickness of approx. 0.1 um and a defect density on the order of 2x10(10) cm-2. The AlN buffer layers contained about an order of magnitude higher defect density relative to GaN. N incorporation efficiencies greater than 41% are achieved using NH3 kinetic energies of 0.40 eV during GaN film growth. A compact arc heated supersonic nozzle has been constructed, tested and used to generate high intensity beams of both atomic nitrogen (N) and electronically excited molecular nitrogen (N2). It has now been run successfully for several hours in both an arc discharge mode as well as a glow discharge mode generating (N2).
Descriptors : *THIN FILMS, *EPITAXIAL GROWTH, *ELECTRON MICROSCOPY, ALUMINUM COMPOUNDS, REAL TIME, ADSORPTION, PLASMAS(PHYSICS), ION BEAMS, MOLECULAR BEAMS, NITRIDES, ELECTRON ENERGY, MASS SPECTROMETERS, GLOW DISCHARGES, SUPERSONIC FLOW, SILICON CARBIDES, JET FLOW, GALLIUM COMPOUNDS, RADIOFREQUENCY GENERATORS, ELECTRIC ARCS.
Subject Categories : Atomic and Molecular Physics and Spectroscopy
Solid State Physics
Distribution Statement : APPROVED FOR PUBLIC RELEASE