Low resistivity ohmic titanium carbide contacts to n- and p-type 4H-silicon carbide

Abstract

Low resistivity Ohmic contacts of epitaxial titanium carbide to highly doped n- (1.3 x 10(19) cm(-3)) and p- (>10(20) cm(-3)) type epilayer on 4H-SiC were investigated. The titanium carbide contacts were epitaxially grown using coevaporation with an e-beam for Ti and a Knudsen cell for C-60 in a UHV system. A comparison of epitaxial evaporated Ti Ohmic contacts on p(+) epilayer of 4H-SiC is also given. The as-deposited TiC Ohmic contacts showed a good Ohmic behavior and the lowest contact resistivity (rho(C)) was 7.4 x 10(-7) Ohm cm(2) at 200 degrees C for n-type, and 1.1 x 10(-4) Ohm cm(2) at 25 degrees C for p-type contacts. Annealing at 950 degrees C did not improve the Ohmic contact to n-type 4H-SiC, but instead resulted in an increase in rho(C) to 4.01 x 10(-5) Ohm cm(2) at 25 degrees C. In contrast to n-type, after annealing at 950 degrees C the specific rho(C) for p-type SiC reached its lowest value of 1.9 x 10(-5) Ohm cm(2) at 300 degrees C. Our results indicate that co-evaporated TiC contacts to n- and p-type epilayers of 4H-SiC should not require a higher post-annealing temperature, contrary to earlier works. Material characteristics, utilizing X-ray diffraction, Low energy electron diffraction, Rutherford backscattering spectrometry, transmission electron microscopy, and X-ray photoelectron spectroscopy measurements are also discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.