Accession Number : ADA317621
Title : Selected Energy Epitaxial Deposition and Low Energy Electron Microscopy of AlN, GaN and SiC Thin Films.
Descriptive Note : Quarterly technical rept. 1 Jul-30 Sep 96,
Corporate Author : NORTH CAROLINA STATE UNIV AT RALEIGH DEPT OF CHEMICAL ENGINEERING
Personal Author(s) : Davis, R. F. ; Lamb, H. H. ; Tsong, I. S. ; Bauer, E. ; Chen, E.
PDF Url : ADA317621
Report Date : SEP 1996
Pagination or Media Count : 31
Abstract : Within the multicenter tight-binding formalism, experimentally determined structural parameters and phonon frequencies of GaN and AlN in both the zinc-blende and the wurtzite phase have been reproduced with an accuracy that is similar to highly converged ab initio calculations. Thus, a reliable basis that allows realistic molecular-dynamics simulations for surface structure calculations and the investigation of the collision dynamics of small molecules on surfaces now exists. Different approaches were attempted to obtain clean, flat, and scratch-free 6H-SiC(0001) substrates for the epitaxial growth of nitride films. LEEM images show that the ex situ high-temperature etching treatment by NASA Lewis produced satisfactory surfaces. An in situ etching/cleaning scheme involving the use of silane gas (SiH4) also produced flat terraces and atomic steps on the 6H-SiC(0001) surface as imaged by STM. The first GaN growth experiments using dual seeded supersonic beams of ammonia and triethylgallium were performed. The initial experiments using hydrogen-passivated Si(100) substrates at 600 deg C were not successful. Growth experiments are continuing using sapphire(0001) substrates. Successful ex situ cleaning and in situ remote plasma nitridation of GaP(100) substrates were examined using AES, XPS and LEED. UV/O3 cleaning followed by etching in either hydrochloric or phosphoric acid was effective in removing C and O contamination from GaP. Subsequent UHV annealing at 800 deg C had little effect on the surface composition. In situ exposure to a remote N2 plasma at 200 deg C for 5 min was effective at removing residual carbon and converting the surface layer to GaN. Deposition of AlN layers on Si(100) has been accomplished with a seeded supersonic molecular beam under conditions suitable for observation in the Low Energy Electron Microscope (LEEM).
Descriptors : *ALUMINUM COMPOUNDS, *THIN FILMS, *NITRIDES, *SILICON CARBIDES, *GALLIUM COMPOUNDS, *MOLECULAR BEAM EPITAXY, ANNEALING, LAYERS, HIGH TEMPERATURE, ZINC SULFIDES, EPITAXIAL GROWTH, SEMICONDUCTORS, ETCHING, AMMONIA, ELECTRON MICROSCOPY, DEPOSITION, ELECTRON ENERGY, SILANES, PHONONS, CLEANING, CONTAMINATION, SUPERSONIC CHARACTERISTICS, COLLISIONS, HYDROCHLORIC ACID, PHOSPHORIC ACIDS, SEEDING.
Subject Categories : Solid State Physics
Distribution Statement : APPROVED FOR PUBLIC RELEASE