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U. Schmid, R. Getto, S.T. Sheppard, W. Wondrak:
"Temperature behavior of specific contact resistance and resistivity on nitrogen implanted 6H-SiC with titanium silicide ohmic contacts";
Journal of Applied Physics, Vol. 85 (1999), 2681 - 2688.

The electrical characteristics of TiSix contacts to nitrogen implanted 6H-SiC are investigated using linear transmission line method structures at temperatures up to 673 K. Nitrogen is implanted into a p-type (NA1 × 1016 cm - 3) 6H-SiC epilayer at 500 °C and activated at 1700 °C, resulting in an activated donor concentration of ND = 5 × 1019 cm - 3 to a depth of 300 nm with a reduced electrically active surface concentration of about ND5 × 1018 cm - 3. Sputtered titanium silicide is used as contact metallization. Five different contact formation temperatures TA ranging from 900 to 1150 °C are applied to the samples in order to investigate the specific contact resistance c. Whereas an anneal of at least 950 °C is necessary to achieve an ohmic contact behavior, samples annealed at 1150 °C show specific contact resistance of 7 × 10-6 cm2 at room temperature, which decreases monotonically to 4 × 10-6 cm2 at 673 K. The sheet resistance Rs (resistivity s) of the n+-implanted layer is 521 / (15.6 × 10-3 cm) at 303 K. Up to 573 K, Rs declines to 354 / (10.6 × 10-3 cm) as the incomplete ionization of the nitrogen dopants dominates the temperature behavior. Above 573 K, the reduction of the electron mobility via phonon scattering dominates, and Rs increases to 363 / (10.9 × 10-3 cm) at 673 K. From the resistivity as a function of temperature, the low field mobility µ0 is 149 cm2/V s at 300 K, and the temperature exponent =1.62 of the power law dependence can be deduced. ©1999 American Institute of Physics.

http://dx.doi.org/10.1063/1.369628