Highly Stable and Non-Volatile Optoelectronic Synapses for Sensing, Memory, and Computing Enabled by a Deep-Potential Floating Gate.

Optoelectronic synapses integrating optical sensing and memory functions are promising building blocks for neuromorphic visual systems. Here, an optoelectronic synaptic transistor based on a MoS2/h-BN/Au heterostructure with Au as the floating gate is demonstrated. Benefiting from the high work function of the metal floating gate (MFG), the device exhibits efficient non-volatile charge storage with a large memory window of 97.6 V and a stored charge density of 7.0 × 1012 cm-2. Under optical stimulation, the device shows pronounced wavelength-dependent synaptic plasticity. The device exhibited data retention exceeding 3000 s and cycling endurance over 1600 programming/erasing cycles. Separately, reproducible programming/erasing operation was observed after 200 days of storage under ambient conditions. In particular, 450 nm illumination generates high-energy photocarriers in the MoS2 channel, which more effectively modulate the charge state of the MFG through carrier transfer across the h-BN barrier, leading to stable long-term potentiation behavior. More importantly, grounding the MFG suppresses the non-volatile optical synaptic response, highlighting the dominant contribution of floating-gate charge storage over interfacial trapping effects. Using experimentally measured weight-update characteristics, a hardware-aware neural-network simulation achieves 98.4% test accuracy on MNIST handwritten-digit classification. This work highlights the potential of the MFG architecture for integrated optoelectronic memory and neuromorphic vision applications.