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Low Temperature Deposition and Characterization of N- and P-Type Silicon Carbide Thin Films and Associated Ohmic and Schottky Contacts.

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Final technical rept. 1 Jan-30 Jun 96,

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Epitaxial, undoped films of 6H-SiC0001 and 3C-SiC111 have been grown by gas source GS MBE on 6H-SiC0001 substrates and 2H-AlN0001 layers between 1050-1250 deg C using SiH4 and C2H4 for Si and C, respectively. Controlled n- and p-type doping was achieved via NH3 and evaporated Al. REED and HRTEM showed the films to be monocrystalline and of either the 6H or 3C polytype. As-deposited at RT NiAl, Au, and Ni contacts were rectifying on p-type 6H-SiC 0001 with very low leakage current densities approx. 1x10exp -8 Asq cm at 10 V. The Schottky barrier heights showed a reduced dependence on the metal work functions, a result which is in agreement with those for n-type SiC. NiNiAl contacts on p 1x10exp 19cu cm SiC were ohmic after annealing for 10-80 s at 1000 deg C in a N2 ambient. The estimated specific contact resistivity was 2-3x10exp -2 ohm sq cm. The high contact resistivities are partly attributed to an insulating oxide layer which formed at the surface of the contacts during the annealing process. Cr-B contacts were semi-ohmic on p-type SiC 1x1018 sq cm after annealing at 1000 deg C for 60-300 s in Ar oxidation of these latter contacts did not occur. AlAlNa-SiC MIS diodes with several AlN thicknesses have been fabricated via GSMBE. C-V measurements at RT between 10 kHz and 1 MHz showed accumulation and depletion over the entire frequency range without dispersion. Inversion was not achieved. Thin layers 1000A of AlN exhibited moderate leakage currents, but thicker layers reduced this problem. Calculated values of the dielectric constant matched the measured values. Results of UV-photoemission spectroscopy UPS, Auger electron spectroscopy, and LEED studies of the surface and interface properties of heteroepitaxial AlN on 6H-SiC grown in situ.

Subject Categories:

  • Inorganic Chemistry
  • Physical Chemistry
  • Electrical and Electronic Equipment
  • Coatings, Colorants and Finishes
  • Crystallography
  • Electricity and Magnetism
  • Atomic and Molecular Physics and Spectroscopy

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