Device Characterization and Design Guideline of Amorphous InGaZnO Junctionless Thin-Film Transistor

Amorphous InGaZnO junctionless thin-film transistors (a-IGZO JL-TFTs) with different active layer thicknesses and thermal treatments were fabricated. The unique feature of a-IGZO JL-TFTs is that all of the active layer and source/drain (S/D) electrodes are realized by the deposition of the InGaZnO thin film. A quantitative analysis to completely deplete the active layer when the device is turned OFF has been performed according to the active layer thickness. The impact of active layer thickness and thermal treatment on the performance of a-IGZO JL-TFTs has been investigated. With the increase in active layer thickness and annealing temperature, the transfer curves shifted to the negative direction. From the effects of S/D series resistance on the performance of a-IGZO JL-TFTs, the series resistance cannot be a serious problem when the contact size is small enough and the active layer is thick enough. To completely deplete the active layer, the impacts of the key device design parameters such as gate oxide thickness, gate workfunction, and high-kappa dielectrics on the device performance have been investigated using device simulation.