Dynamic Response of Normal and Corbino a-Si:H TFTs for AM-OLEDs

The dynamic characteristics of normal and Corbino hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) have been investigated. Top- and bottom-gate normal a-Si:H TFTs and bottom-gate Corbino a-Si:H TFTs were fabricated with a five-photomask process used in the processing of the active-matrix liquid crystal displays. The charging time and feedthrough voltage DeltaVPmeasurement indicates that the normal a-Si:H TFT shows a similar behavior regardless of its TFT geometrical structure. Using a simple gate-to-source capacitance CGSmodel, the dependence of DeltaVPon gate-to-source overlap and storage capacitor has closely been estimated using analytical calculation. Due to a unique electrode geometry, the Corbino a-Si:H TFT shows a small deviation from an analytical model used for the normal a-Si:H TFT, and consequently, a modified analytical model was developed. We also developed concepts of its possible application as a switching device to active-matrix organic light-emitting displays.