Metastability of hot-wire amorphous-silicon thin-film transistors

Abstract Defect-state creation in hydrogenated amorphous-silicon causes a threshold-voltage shift in thin-film transistors (TFTs) after gate-voltage stress. We studied this metastable effect in transistors based on silicon deposited by hot-wire chemical vapor deposition. Amorphous as well as heterogeneous silicon, incorporating some fraction of crystallites were used. We demonstrate that such TFTs have a performance with a field-effect mobility of 1.4 cm2/V s in an inverted-staggered structure. A threshold-voltage of 4.6 V was found for TFTs based on heterogeneous silicon deposited on silicon oxide. The threshold-voltage shift in these TFTs could be fitted with the same function as for amorphous-silicon TFTs. All hot-wire TFTs had a stability better than that of state-of-the-art devices prepared by plasma-enhanced chemical vapor deposition (PECVD).