UV light-induced graphene/GaN heterojunction photomemory devices with negative photocurrent

Synaptic devices inspired by biological systems have the potential to overcome the limitations of traditional computers based on von Neumann architecture. There have been attempts to use GaN as a synaptic device, but it is challenging due to the short decay time caused by rapid recombination, despite the presence of trap sites within the GaN. In this study, we present a graphene/GaN optoelectronic synaptic device that controls current weights using ultraviolet light. Through photoluminescence measurements, we reveal that graphene can promote efficient separation of electron-hole pairs in GaN, which in turn suppresses recombination and extends the carrier decay time. Building on this mechanism, our results show that graphene/GaN optoelectronic synaptic devices are capable of not only emulating a range of biologically inspired synaptic behaviors but also memorizing letter patterns.