Device performances and instabilities of the engineered active layer with different film thickness and composition ratios in amorphous InGaZnO thin film transistors

The device performances and instabilities of the engineered active layer with different film thickness and composition ratios in amorphous InGaZnO thin film transistor prepared by RF-sputtering have been investigated. The engineered active layer devices were composed of an In and Zn rich front layer with thickness of 10 nm and a Ga rich back layer with thickness from 20 to 30 nm. The device instabilities were investigated under positive bias stress (PBS), negative bias illumination stress (NBIS) and high [V.sub.GS] and [V.sub.DS] stress. The device performances and the stability have been enhanced in channel engineered active layer a-IGZO TFTs due to the combination of the high conductive channel with In and Zn rich front layer and the passivation effects with the Ga rich back layer. The concurrent device degradation mechanism is suggested to explain the more severe device degradation under high [V.sub.GS] and [V.sub.DS] stress than the device degradation under PBS. Keywords: InGaZnO thin film; composition ratio; film thickness; instability