Reconfigurable Physical Reservoir in GaN/α-In₂Se₃ HEMTs Enabled by Out-of-Plane Local Polarization of Ferroelectric 2D Layer

Abstract

Significant effort for demonstrating a gallium nitride (GaN)-based ferroelectric metal-oxide-semiconductor (MOS)-high-electron-mobility transistor (HEMT) for reconfigurable operation via simple pulse operation has been hindered by the lack of suitable materials, gate structures, and intrinsic depolarization effects. In this study, we have demonstrated artificial synapses using a GaN-based MOS-HEMT integrated with an α-In₂Se₃ ferroelectric semiconductor. The van der Waals heterostructure of GaN/α-In₂Se₃ provides a potential to achieve high-frequency operation driven by a ferroelectrically coupled two-dimensional electron gas (2DEG). Moreover, the semiconducting α-In₂Se₃ features a steep subthreshold slope with a high ON/OFF ratio (∼10¹⁰). The self-aligned α-In₂Se₃ layer with the gate electrode suppresses the in-plane polarization while promoting the out-of-plane (OOP) polarization of α-In₂Se₃, resulting in a steep subthreshold slope (10 mV/dec) and creating a large hysteresis (2 V). Furthermore, based on the short-term plasticity (STP) characteristics of the fabricated ferroelectric HEMT, we demonstrated reservoir computing (RC) for image classification. We believe that the ferroelectric GaN/α-In₂Se₃ HEMT can provide a viable pathway toward ultrafast neuromorphic computing.