Improved electrical stability in asymmetric fingered polysilicon Thin Film Transistors

Recently, we proposed asymmetric fingered polysilicon thin film transistors, where the transistor channel region is split into two zones with different lengths separated by a floating n(+) region, which allows an effective reduction of the kink effect. In this work, we analysed the experimental electrical characteristics by using numerical simulations for a specific channel configuration and then we studied the effects of prolonged bias stress on these devices and conventional non self-aligned thin film transistors. We found that asymmetric fingered transistors are characterized by a substantial reduction of the transconductance degradation induced by hot carrier effect, if compared to conventional thin film transistors. By modeling the device with two transistor in series, we could explain the reduced effects of hot carrier-induced degradation.