Accession Number : ADA337629

Title :   Research Related to the Development, Fabrication and Characterization of UV Detectors and Cold Cathode Devices

Descriptive Note : Annual technical rept. 1 Jan-31 Dec 97

Corporate Author : NORTH CAROLINA STATE UNIV AT RALEIGH

Personal Author(s) : Davis, R. F.

PDF Url : ADA337629

Report Date : DEC 1997

Pagination or Media Count : 48

Abstract : The microstructure and the mechanism of lateral epitaxy overgrowth (LEO) of homoepitaxially and selectively grown GaN pyramid structures on GaN/AlN/6H-SiC(0001) substrates and within windows in SiO2 masks have been investigated by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The structures were produced by organometallic vapor phase epitaxy (OMVPE) for field emission studies. The SiO2 film provided an amorphous stage on which lateral growth of the GaN occurred. Essentially no GaN deposited on the SiO2 because of the substantial differences in sticking coefficients of Ga and N species on GaN (s=l) and SiO2 (s approx. 0). LEO of GaN layers has been achieved on 3 micrometers wide and 7 micrometers spaced stripe windows contained in SiO2 masks. A high density of threading dislocations, originating from the interface of the underlying GaN with the AlN buffer layer, were contained in the GaN grown in the window regions. The overgrowth regions, by contrast, contained a very low density of dislocations. The second lateral epitaxial overgrowth layers were obtained on the first laterally grown layers by the repetition of SiO2 deposition, lithography and lateral epitaxy. A GaN and Al(x)Ga(1-x)N thin film MODFET structure was grown for Northrup Grumman. The microstructures and photoluminescence spectra have been determined for In(x)Ga(1-x)N films (x </= approx. 0.23) grown on substrates of alpha(6H)-SiC(0001) wafer/AlN buffer layer/GaN heterostructures by low pressure OMVPE at 780 deg C using nitrogen as the diluent and carrier gas and V/III ratios as low as 2,420. Indium droplets were not observed.

Descriptors :   *ULTRAVIOLET DETECTORS, *COLD CATHODE TUBES, BUFFERS, SCANNING ELECTRON MICROSCOPES, MICROSTRUCTURE, LAYERS, SILICON DIOXIDE, PHOTOLUMINESCENCE, THIN FILMS, LOW PRESSURE, ORGANOMETALLIC COMPOUNDS, EPITAXIAL GROWTH, SUBSTRATES, AMORPHOUS MATERIALS, VAPOR PHASES, NITRIDES, NITROGEN, GASES, ELECTRON MICROSCOPY, LITHOGRAPHY, FIELD EMISSION, SPECTRA, DISLOCATIONS, ALUMINUM, DROPS, HIGH DENSITY, HETEROGENEITY, LOW DENSITY, INDIUM, SILICON CARBIDES, MASKS, GALLIUM COMPOUNDS.

Subject Categories : Inorganic Chemistry
      Electrical and Electronic Equipment
      Ultraviolet Detection and Detectors
      Crystallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE