An All-in-One Biomimetic 2D Spiking Neural Network

Abstract In spite of recent advancements in bio-realistic artificial neural networks such as spiking neural networks (SNNs), the energy efficiency, multifunctionality, adaptability, and integrated nature of biological neural networks (BNNs) largely remain unimitated in hardware neuromorphic computing systems. Here we exploit optoelectronic and programmable memory devices based on emerging two-dimensional (2D) layered materials such as MoS2 to demonstrate an “all-in-one” hardware SNN system which is capable of sensing, encoding, unsupervised learning, and inference at miniscule energy expenditure. In short, we have utilized photogating effect in MoS2 based neuromorphic phototransistor for sensing and direct encoding of analog optical information into graded spike trains, we have designed MoS2 based neuromorphic encoding module for conversion of spike trains into spike-count and spike-timing based programming voltages, and finally we have used arrays of programmable MoS2 non-volatile synapses for spike-based unsupervised learning and inference. We also demonstrate adaptability of our SNN for learning under scotopic (low-light) and photopic (bright-light) conditions mimicking neuroplasticity of BNNs. Furthermore, we use our hardware SNN platform to show learning challenges under specific synaptic conditions, which can aid in understanding learning disabilities in BNNs. Our findings highlight the potential of in-memory computing and sensing based on emerging 2D materials, devices, and circuits not only to overcome the bottleneck of von Neumann computing in conventional CMOS designs but also aid in eliminating peripheral components necessary for competing technologies such as memristors, RRAM, PCM, etc. as well as bridge the understanding between neuroscience of learning and machine learning.