Enhanced Current Drive of Double-Gate α-IGZO Thin-Film Transistors

Due to the degradation by hydrogen, the mobilities near the top and bottom insulator/channel interfaces are lower than those at the central amorphous In-Ga-Zn-O (α-IGZO) channel, reflecting the mobilities of 10.2, 7.5, and 1.8 cm2/V·s for double-gate (DG), bottom-gate, and top-gate operations, respectively. DG operation can push more electrons into the central channel than single-gate (SG) operation. Based on the secondary ion mass spectroscopy, hydrogen has a higher concentration near the top and bottom interfaces than at the central region. Based on the first-principle calculations, the hydrogen can form shallow donor states and degrade the mobility of α-IGZO thin-film transistors. The DG operation also creates a larger lateral electric field along the channel direction than SG operation. Both mobility enhancement and lateral electric field increase lead to significant drive current enhancement.