Scandium Nitride as a Gateway III-Nitride Semiconductor for both Excitatory and Inhibitory Optoelectronic Artificial Synaptic Devices

Abstract

Traditional computation based on von Neumann architecture is limited by time and energy consumption due to data transfer between the storage and the processing units. The von Neumann architecture is also inefficient in solving unstructured, probabilistic, and real-time problems. To address these challenges, a new brain-inspired neuromorphic computational architecture is required. Due to the absence of resistance–capacitance delay, high bandwidth, and low power consumption, optoelectronic artificial synaptic devices are highly attractive. Yet, stable, scalable, and complementary metal–oxide–semiconductor (CMOS)-compatible materials exhibiting both inhibitory and excitatory optoelectronic synaptic functionalities have not been demonstrated. Here, epitaxial CMOS-compatible scandium nitride (ScN) optoelectronic artificial synaptic devices that emulate both inhibitory and excitatory biological synaptic activities are presented. The negative and positive persistent photoconductivity of undoped and magnesium-doped ScN is equated to the inhibitory and excitatory synaptic plasticity, respectively, which leads to functionalities like learning–forgetting, frequency-selective optical filtering, frequency-dependent potentiation and depression, Hebbian learning, and logic-gate operations. Temperature-dependent photoresponse and photo-Hall measurements reveal that scattering of photogenerated carriers from charged defect centers results in negative photoconductivity in undoped degenerate ScN. This work opens up the possibility of utilizing a group-III epitaxial semiconducting nitride material with inhibitory and excitatory optoelectronic synaptic functionalities for practical neuromorphic applications.