Ultra-sensitive broadband photoresponse realized in epitaxial SnSe/InSe/GaN heterojunction for light adaptive artificial optoelectronic synapses

By integrating sensing, memory, and computing functions within a single unit, the neuromorphic device enables brain-like computing that could facilitate artificial intelligence applications due to its superior scalability and efficiency. As an emerging form of neuromorphic devices, optoelectronic synapses for artificial visual perception with high optical sensing performance and tunable memory time are highly desired. Herein, we report a new design of ultra-sensitive broadband artificial optoelectronic synapses based on a tailored hybrid heterostructure of epitaxial SnSe/InSe/GaN multilayers, in which the interlayer InSe has been employed as the functional layer. Specifically, InSe plays the crucial role of charge trapping layer by blocking the thermally excited carriers in the potential well, thus an ultra-low dark current in 10⁻¹⁰ A level has been realized under the bias of −1.5 V. Moreover, the InSe layer could significantly extend the photocurrent decay time, which enabled the synaptic functions in the devices. Such multilayer heterojunctions exhibit a broadband photoresponse spanning from the near-infrared to the ultraviolet, with a specific detectivity up to 1.07×10¹¹ Jones under 365 nm excitation. Combining all these merits, light adaptive artificial optoelectronic synapses with multi-color stimuli perception capability have been demonstrated. These results provide a novel and promising strategy for future applications in artificial vision systems.