Scaling of a-InGaZnO TFTs and pixel electrode for AM-LCDs

The channel length (L) and width (W) scaling behavior of amorphous In-Ga-Zn-O thin-film transistors (TFTs) have been investigated. The fabricated TFTs have a mobility of ∼12 cm2/V-s, sub-threshold slope (S) of ∼110 mV/decade, threshold voltage around 0.3 V and off-current below 10−13 A. Even though the TFTs with smaller channel length (L ≤ 5 μm) show proper switching characteristics, threshold voltage lowering and sub-threshold slope degradation are observed, while off-current and mobility are not changed. The mobility degradation with L, which was observed in amorphous silicon TFTs, is not seen for short channel a-IGZO TFTs. Lastly, the necessity of the TFT scaling for a pixel electrode in AM-LCD applications is discussed.