Asymmetric fingered polysilicon p-channel thin film transistor structure for kink effect suppression

We present, for the first time, the application of the asymmetric fingered thin film transistor (AF-TFT) architecture to self-aligned p-channel TFTs for kink effect suppression. In AF-TFT the transistor channel region is split into two zones with different lengths (L1 > L2) separated by a floating p+ region. A fourth electrode, contacting the floating p+ region, allowed us to measure the individual electrical characteristics of the two sub-TFTs. Output characteristics show that substantial kink effect reduction can be achieved when the sub-TFT placed at the drain end of the device has an L2 ≪ L1. The electrical characteristics were analysed by using numerical simulations in the framework of the two-transistor model and we show that kink effect suppression arises from the operation in saturation regime of the source sub-TFT. The electrical characteristics of the fabricated p-channel AF-TFTs show a complete kink effect suppression, making these devices very attractive for current drivers in organic light emitting displays.