Dipole-Enhanced Low Thermal Budget Amorphous InWO TFT Achieving a Steep Subthreshold Swing of 40 mV/Decade Without Ferroelectric Layer

Abstract

This work demonstrates a low thermal budget amorphous InWO ( $\alpha $ -IWO) thin film transistor (TFT) achieving a subthreshold swing (S.S.) of 40 mV/decade without utilizing a ferroelectric gate oxide. The oxygen vacancies in $\alpha $ -IWO induce the formation of an interfacial dipole layer at the surface between $\alpha $ -IWO and SiO2/HfO2. The TFT with dipole-rich interface exhibits the S.S. value below 60 mV/decade over 2 decades of drain current. X-ray diffraction (XRD) confirmed the absence of the ferroelectric orthorhombic phase in the HfO2 layer. Besides, the low thermal budget $\alpha $ -IWO TFT also exhibits a high field effect mobility of 97 cm2/V $\cdot $ s and a large on/off current ratio of 1.8E6, while the process temperature is as low as $300~^{\circ }$ C.