High field-effect-mobility a-Si:H TFT based on high deposition-ratePECVD materials

The hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFT's) having a field-effect mobility of 1.45 ±0.05 cm² /V·s and threshold voltage of 2.0±0.2 V have been fabricated from the high deposition-rate plasma-enhanced chemical vapor deposited (PECVD) materials. For this TFT, the deposition rates of a-Si:H and N-rich hydrogenated amorphous silicon nitride (a-SiN_1.5 :H) are about 50 and 190 nm/min, respectively. The TFT has a very high ON/OFF-current ratio (of more than 10⁷), sharp subthreshold slope (0.3±0.03 V/decade), and very low source-drain current activation energy (50±5 meV). All these parameters are consistent with a high mobility value obtained for our a-Si:H TFT structures. To our best knowledge, this is the highest field-effect mobility ever reported for an a-Si:H TFT fabricated from high deposition-rate PECVD materials