Contact resistivity of Re, Pt and Ta films on n-type β-SiC: Preliminary results

Contact resistivities of as-deposited and annealed Pt, Re and Ta films on n-type single-crystalline β-SiC(001) are characterized using a circular contact pattern and the circular transmission-line model method. The β-SiC substrates used in the experiment are n-type doped either non-intentionally to a carrier concentration of about 1017 cm−3, or by nitrogen implantation and annealing to a concentration of 5 × 1019 cm−3. The effect of a finite resistance along the circular contact rings on the measured potentials is corrected with a resistance network model. non-intentionally doped β-SiC substrates, Pt contacts are non-ohmic regardless of the heat treatment. The as-deposited Ta and Re contacts are ohmic with contact resistivities of 5 × 10−5 Ω cm2 and 4 × 10−4 Ω cm2 respectively. Upon annealing at 500 °C for 30 min, the resistivity of Ta increases slightly while that of Re decreases slightly. Both Ta and Re contacts become non-ohmic by annealing at 900 °C for 30 min. -deposited Ta, Pt and Re contacts are all ohmic on the nitrogen-implanted β-SiC substrate. The contact resistivity of the as-deposited Ta contact is the lowest and in the order of high 10−7 Ω cm2, stays about the same at 500 °C and degrades to 4.3 × 10−6 Ω cm2 at 1000 °C. The as-deposited Re contact has the highest contact resistivity of 1 × 10−4 Ω cm2 but it improves to 1 × 10−5 Ω cm2 upon annealing at 900 °C. The contact resistivity of the as-deposited Pt contacts is 6 × 10−6 Ω cm2 and increases to 1 × 10−5 Ω cm2 at 500 °C. After annealing at 900 °C for 30 min, the Pt contact on the nitrogen-implanted β-SiC is no longer ohmic. The results are compared with the reactions that take place in those systems.