Electrical response of MOSiC gas sensors to CO, NO/sub 2/ and C/sub 3/H/sub 8/

The behaviour as high temperature gas sensors of MOS capacitors and tunnel MOS diodes with Pt/TaSi/sub x/ catalytic gates fabricated on 6H-SiC substrates is presented. The electrical characterization of the both types of devices as a function of the operating temperature and in the presence of gases CO, NO/sub 2/ and C/sub 3/H/sub 8/ has been performed. The best results have been obtained for MOS capacitors after their annealing in alternate pulses of 1% C/sub 3/H/sub 8/ and 1% O/sub 2/ at temperatures between 300 and 500/spl deg/C. Their maximum response has been 80 mV to 1000 ppm of CO at 250/spl deg/C and 71 mV to 10 ppm of NO/sub 2/ at 310/spl deg/C. On the other hand, the tunnel MOS diodes show worse sensitive to these gases, with a maximum response of 1 mV to 1000 ppm of CO at 250/spl deg/C and 600 /spl mu/V to 10 ppm of NO/sub 2/ at 310/spl deg/C.