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.

An artificial synaptic device based on 1,2-diphenylacetylene with femtojoule energy consumption for neuromorphic computing

“…5f shows the confusion matrix of the network, which compares the computational results of the network with the labels of the test set, comprehensively showing the classification effect of the network. 34,58 Table 1 shows a comparison of parameters and functions of several organic synaptic devices. These results demonstrate the advantages of the DPA device in neural networks.…”

Multifunctional Two-Terminal Optoelectronic Synapse Based on an Organic Semiconductor Film

“…To date, optoelectronic devices have successfully replicated important functions of biological synapses, including excitatory postsynaptic current (EPSC)/inhibitory postsynaptic current (IPSC), short-term plasticity (STP)/long-term plasticity (LTP), and so on. – However, many of the reported artificial synapses are based on fragile inorganic materials, which generally require complex and expensive preparation methods and are unlikely to work well for large-scale and flexible optoelectronic synaptic devices. – , On the other hand, the quick development of wearable electronics puts a strong demand on flexible computing systems. Thus, great efforts have been made to explore flexible organic materials for synaptic devices. – Until now, a variety of organic materials have been successfully utilized for the fabrication of optoelectronic synapses, such as chitosan, chlorophyll, copper­(II) phthalocyanine (CuPc), , pentacene, poly­(3-hexylthiophene) (P3HT), , and poly­(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS). , However, in most cases, these devices were constructed on rigid substrates, failing to fully exploit the flexible nature of these organic materials. ,– …”

“…21−26 However, many of the reported artificial synapses are based on fragile inorganic materials, which generally require complex and expensive preparation methods and are unlikely to work well for large-scale and flexible optoelectronic synaptic devices. [21][22][23][24][25]27 On the other hand, the quick development of wearable electronics puts a strong demand on flexible computing systems. Thus, great efforts have been made to explore flexible organic materials for synaptic devices.…”

Bidirectional Synaptic Phototransistor Based on Two-Dimensional Ferroelectric Semiconductor for Mixed Color Pattern Recognition

“…For example, negative synaptic weight updates have been demonstrated in black phosphorus (BP) by forming oxidation-related defects and creating charge traps. − Semiconductor heterostructures have been employed to realize bidirectional synaptic modulation, exploiting the carriers trapping and detrapping at the heterointerface. − Despite these advances, the environmental instability of BP leads to the degradation of device performance, and heterostructures struggle to achieve fine control of synaptic weight due to metastable traps, overshadowing their further applications. In this regard, the emerging two-dimensional (2D) ferroelectric semiconductor α-In 2 Se 3 , with its coupled ferroelectric and semiconductor properties and appropriate bandgap for photosensing, appears to be a superior candidate for multifunctional optoelectronics. − Despite optoelectronic synaptic capabilities that have been demonstrated in α-In 2 Se 3 -based devices, the optical pulse stimulation only induced potentiated synaptic weight update, rendering them less advantageous in artificial vision systems. − …”