Boost up the electrical performance of InGaZnO thin film transistors by inserting an ultrathin InGaZnO:H layer

This study examined the electrical performance of bilayer channel InGaZnO:H/InGaZnO thin-film transistors (TFTs). The field-effect mobility and bias stress stability of the InGaZnO device were improved by inserting the hydrogenated InGaZnO ultrathin layer compared to the pure InGaZnO single channel layer device. As a consequence, a high field-effect mobility of 55.3 cm2/V s, a high on/off current ratio of 108, a threshold voltage of 0.7 V, and a small sub-threshold swing of 0.18 V/decade have been achieved. The X-ray photoelectron spectroscopy and low-frequency noise analysis suggest that these desirable properties should be attributed to the ultrathin InGaZnO:H layer, which could provide suitable carrier concentration and reduce the average trap density near the channel and insulator layer interface. Meanwhile, the channel conductance of the bilayer device is controlled by thick InGaZnO layer through formation barrier energy for electron transport at the interface of InGaZnO:H and InGaZnO layer. These improved electrical properties have represented a great step towards the achievement of transparent, high performances, and low-cost metal oxide TFTs.