Accession Number : ADA300928

Title :   Defects and Impurities in 4H- and 6H-SiC Homoepitaxial Layers: Identification, Origin, Effect on Properties of Ohmic Contacts and Insulating Layers and Reduction.

Descriptive Note : Quarterly technical rept. 17 Jul-30 Sep 95,

Corporate Author : NORTH CAROLINA STATE UNIV AT RALEIGH

Personal Author(s) : Davis, R. F. ; Aboelfotoh, M. O. ; Nemanich, B. J. ; McLarty, P. K. ; O'Brien, M.

PDF Url : ADA300928

Report Date : SEP 1995

Pagination or Media Count : 30

Abstract : The design and construction of a new and unique CVD system for the deposition and analysis of SiC thin films is underway. Initial measurements of the impact ionization coefficients of electrons and holes in SiC devices have been made. Degradation in breakdown voltage and an increase in the leakage current were observed. Analytical expressions were derived for the extraction of impact ionization coefficients from I-V data. Simulations were performed for a simple p-n junction diode, with and without impact ionization, and impact ionization coefficients were extracted using the analytical expressions derived. NiAl contacts with Ni passivating layers were deposited at room temperature on p-type 6H-SiC (0001) substrates. As-deposited contacts were rectifying with very low leakage current densities (approx. 1 x 10( exp -8 A/sq cm at 10 V), ideality factors between 1.4 and 2.4, and a Schottky barrier height (SBH) of approximately 1.37eV. The contacts on p+ (1 x 10(exp 19.cu cm) were ohmic after annealing for 10-80 s at 1000 deg C in a N2 ambient. The estimated specific contact resistivity from a non-mesa etched TLM pattern was 2-3 x 10(exp- 2 ohms sq cm. The Ni/NiAl contacts deposited on SiC with lower carrier concentrations (1-5 x 10( exp 18 / cu cm) were not ohmic after annealing at 1000 deg C for 10-60 s but became nearly ohmic after annealing for 80 s. As-deposited Ni and Au contacts on p-type 6H-SiC displayed similar current-voltage characteristics with calculated SBH's of 1.31 and 1.27eV, respectively. jg p.2

Descriptors :   *LAYERS, *INSULATION, *CHEMICAL VAPOR DEPOSITION, *IMPURITIES, *SCHOTTKY BARRIER DEVICES, *SILICON CARBIDES, DIODES, ANNEALING, IMPACT, DEGRADATION, RESISTANCE, THIN FILMS, VOLTAGE, CHARGE CARRIERS, EPITAXIAL GROWTH, SUBSTRATES, ROOM TEMPERATURE, ESTIMATES, REDUCTION, ELECTRONS, DEFECTS(MATERIALS), MATHEMATICAL ANALYSIS, LOW LEVEL, CONCENTRATION(COMPOSITION), IONIZATION, NICKEL, N TYPE SEMICONDUCTORS, ELECTRIC CURRENT, LEAKAGE(ELECTRICAL), GOLD, HEIGHT, BREAKDOWN(ELECTRONIC THRESHOLD), P TYPE SEMICONDUCTORS, ELECTRIC CONTACTS, ALUMINIDES, JUNCTION DIODES.

Subject Categories : Inorganic Chemistry
      Electrical and Electronic Equipment
      Electrooptical and Optoelectronic Devices
      Electricity and Magnetism

Distribution Statement : APPROVED FOR PUBLIC RELEASE