Dimensional effects on the drain current of N- and P-channel polycrystalline silicon thin film transistors

N-channel and p-channel polysilicon thin film transistors (poly-Si TFTs) with different geometries were fabricated and characterized to study the interactive effects of active channel area on drain current. We find that for both non-passivated and passivated p-TFTs, since no avalanche multiplication is involved, the drain current is increased with reduced active channel area due to the reduction of grain-boundary trap density. In contrast, a somewhat unexpected trap dependence of the kink effect is observed in n-TFTs. Consequently, the dependence of active channel area on drain current differs between non-passivated n-TFTs with large trap density and passivated n-TFTs with small trap density.