Electrical features of an amorphous indium-gallium-zinc-oxide film transistor using a double active matrix with different oxygen contents

The electrical characteristics of amorphous indium-gallium-zinc-oxide (a-IGZO) thin film transistors (TFTs) are systematically studied using a double a-IGZO active layer that is composed of a-IGZOx (oxygen-ion-poor region) and a-IGZOy (oxygen-ion-rich-region). An active layer is designed to have a serially-stacked bi-layer matrix with different oxygen contents, providing the formation of different electron conduction channels. Two different oxygen contents in the active layer are obtained by varying the O2 partial pressure during sputtering. The a-IGZO TFT based on a double active layer exhibits a high mobility of 9.1 cm2/Vsec, a threshold voltage (VT) of 16.5 V, and ΔVT shifts of less than 1.5 V under gate voltage stress. A possible electrical sketch for the double active layer channel is also discussed.