Enhanced Electrical Polarization in van der Waals α-InSe Ferroelectric Semiconductor Field-Effect Transistors by Eliminating Surface Screening Charge.

A van der Waals (vdW) α-InSe ferroelectric semiconductor channel-based field-effect transistor (FeS-FET) has emerged as a next-generation electronic device owing to its versatility in various fields, including neuromorphic computing, nonvolatile memory, and optoelectronics. However, screening charges cause by the imperfect surface morphology of vdW α-InSe inhibiting electrical polarization remain an unresolved issue. In this study, for the first time, a method is elucidated to recover the inherent electric polarization in both in- and out-of-plane directions of the α-InSe channel based on post-exfoliation annealing (PEA) and improve the electrical performance of vdW FeS-FETs. Following PEA, an ultra-thin InSeO layer formed on the top surface of the α-InSe channel is demonstrated to passivate surface defects and enhance the electrical performance of FeS-FETs. The on/off current ratio of the α-InSe FeS-FET has increased from 5.99 to 1.84 × 10, and the magnitude of ferroelectric resistance switching has increased from 1.20 to 26.01. Moreover, the gate-modulated artificial synaptic operation of the α-InSe FeS-FET is demonstrated and illustrate the significance of the engineered interface in the vdW FeS-FET for its application to multifunctional devices. The proposed α-InSe FeS-FET is expected to provide a significant breakthrough for advanced memory devices and neuromorphic computing.