Photoinduced top-gate effect in amorphous InGaZnO4 thin-film transistors

In this paper, we will discuss the top-gate effect under illumination in amorphous InGaZnO4 thin-film transistors (a-InGaZnO TFTs) having a transparent top-gate electrode. The dependence of bottom-gate transfer characteristics on top-gate voltage (V-tg) shows a specific behavior under 425nm light illumination, which we call the photoinduced top-gate effect. The subthreshold current under 425nm light illumination, whose photon energy is smaller than the optical bandgap of a-InGaZnO, increases with increasing magnitude of negative V-tg. Measurements at various temperatures support the idea that the photoinduced top-gate effect arises from a tunneling mechanism due to a negative V-tg. (C) 2016 The Japan Society of Applied Physics