The experimental results regarding to the effects of ultraviolet (UV) light illumination on the characteristics of hydrogenated amorphous silicon (a-Si:H) thin film transistors (TFT's) have been presented. The device parameters of a-Si:H TFT, such as threshold voltage, field-effect mobility, and subthreshold slope, have been degraded by electrical stress and visible light illumination, but substantially improved by UV radiation. This may be attributed to an annealing effect on the dangling-bond defects, involving a number of phonons generated by absorption of high energy UV photons in the a-Si:H TFT channel. It has been also observed that the off-current of a-Si:H TFT decreases remarkably while the on-current changes very little. From the experimental results, we report that the improved on/off current ratio of a-Si:H TFT may be achieved by UV radiation.
We presents a new model for the series resistance of an amorphous silicon (a-Si) thin film transistor (TFT) with an inverted-staggered configuration, considering the current spreading under the source and the drain contacts as well as the space charge limited current. The calculated results of our model have been in good agreements with the measured data over a wide range of applied voltage, gate-to-source and gate-to-drain overlap length, channel length, and operating temperature. Our model shows that the relative contribution of the series resistances to the current-voltage (I-V) characteristics of the a-Si TFT in the linear regime is more significant at low drain and high gate voltages, for short channel and small overlap length, and at low operating temperature, which has been verified successfully by the experimental measurements.
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