Accession Number : ADA328552

Title :   Selected Energy Epitaxial Deposition and Low Energy Electron Microscopy of AlN, GaN and SiC Thin Films.

Descriptive Note : Quarterly technical rept. 1 Apr-30 Jun 97,

Corporate Author : NORTH CAROLINA STATE UNIV AT RALEIGH DEPT OF MATERIALS SCIENCE AND ENGINEERING

Personal Author(s) : Davis, R. F. ; Lamb, H. H. ; Tsong, I. S. ; Bauer, E. ; Chen, E.

PDF Url : ADA328552

Report Date : JUN 1997

Pagination or Media Count : 28

Abstract : Tight-binding ab initio molecular dynamics simulations involving a generalized multicenter tight-binding formalism which includes self-consistent charge transfer between the ions were used to investigate initial stages of growth of Group III nitrides. Initial results for the lattice constants, bulk modulus, phonon frequencies and electronic structure of the zincblende and wurtzite phase of bulk GaN and AlN are in good agreement with existing experimental data and highly converged plane wave calculations. The calculated relaxation parameters and formation energies determined for stoichiometric and nonstoichiometric geometries agree very well with density-functional calculations. Vacancy structures are the most stable configurations on the anion and cation terminated surfaces. The effectiveness of a supersonic seeded-beam jet and an RF plasma, connected independently to a low energy electron microscope (LEEM), were compared as sources of nitrogen for the growth of gallium nitride films on 6H-SiC(0001) substrates. Growth of GaN films on chemically vapor deposited GaN/AlN/SiC substrates was accomplished using triethylgallium and NH3-seeded supersonic molecular beams. The films were characterized by XPS, RHEED, SEM and AFM, and the effects of substrate temperature, NH3 flux and Ga flux on growth rate and film morphology examined. Typical GaN films grown at 700 deg C under NH3-limited conditions exhibited a rough, highly faceted surface morphology; smoother surfaces are obtained when the Ga flux was increased. Nitridation experiments on Si(100) wafers were conducted using monoenergetic and mass separated ion beams of N2(+) and N(+) produced in colutron ion sources. SIMS studies of the surfaces nitrided with both ions reveal slowly decaying nitrogen signals due to formation of SiN layers. Research is underway to deposit GaN layers by Ga(+) and N2(+) (or N(+)) beams.

Descriptors :   *EPITAXIAL GROWTH, *ELECTRONIC STATES, SCANNING ELECTRON MICROSCOPES, FLUX(RATE), PLASMAS(PHYSICS), THIN FILMS, CHEMICAL VAPOR DEPOSITION, NITRIDES, NITROGEN, SURFACE PROPERTIES, LOW ENERGY, NITRIDING, CHARGE TRANSFER, GROUP III COMPOUNDS, PHONONS, SUPERSONIC CHARACTERISTICS, RADIOFREQUENCY, MOLECULAR PROPERTIES, SILICON CARBIDES, PLANE WAVES, GALLIUM COMPOUNDS, BULK MODULUS.

Subject Categories : Crystallography
      Solid State Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE