Low Temperature Deposition and Characterization of N- and P-Type Silicon Carbide Thin Films and Associated Ohmic and Schottky Contacts.
Abstract
Epitaxial, undoped films of 6H-SiC(0001) and 3C-SiC(111) have been grown by gas source (GS) MBE on 6H-SiC((0001) substrates and 2H-AlN(0001) 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. 1x10(exp -8) A/sq 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. Ni/NiAl contacts on p+ (1x10(exp 19/cu cm) SiC were ohmic after annealing for 10-80 s at 1000 deg C in a N2 ambient. The estimated specific contact resistivity was 2-3x10(exp -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. Al/AlN/a-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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1996
- Accession Number
- ADA310905
Entities
People
- M. C. Benjamin
- Robert F Davis
- Robert J. Nemanich
- S. Kern
- S. W. King
Organizations
- North Carolina State University