Hydrogenated n-Channel Low Temperature Polycrystalline Silicon TFTs as Ultraviolet Dosimeters

N-channel thin film transistors (TFTs) fabricated with hydrogenated low temperature polycrystalline silicon (LTPS) were exposed to ultraviolet (UV) radiation to a cumulative dose up to 16 J/cm ² . The effect of radiation on the electrical characteristics of the devices was monitored after the irradiation steps and in a prolonged period after irradiation. The main monitoring parameter was the threshold voltage ( V _th ) which was found to have exponentially linear dependence on irradiation dose. This, together with obtained low fading, suggests that hydrogenated n-channel low temperature polycrystalline silicon TFTs have potential as UV radiation dosimeters. In addition, the physical mechanisms of the UV induced electrical degradation were analyzed in terms of the radiation generated traps at poly-Si grain boundary and poly-Si and gate oxide insulator (poly-Si/SiO ₂ ) interface.