Group‐III Nitride‐Based Wide‐Spectrum Multifunctional Synapses for Encrypted Light Communication and Image Recognition

Developing multifunctional photoelectric synapses provides an effective solution for further improving the computational speed and integration of chips. However, conflicts in working mechanisms between photodetection and photoelectric synapses block the way to achieve both high responsivity and significant synaptic characteristics. In this work, InGaN core-shell nanorods-based wide-spectrum multifunctional synapses with an ultrathin oxide layer have been designed and prepared. Validated through multiple characterization techniques and density functional theory (DFT) calculation, the trap levels introduced by the oxide layer enable the regulation of the carrier relaxation time. Benefiting from both gradient indium composition and tunable carrier relaxation time, multifunctional integration of wide-spectrum response and synaptic plasticity is achieved, which allows the synapses to switch by merely modulating the incident light wavelength. In photodetector mode, the synapses have a wide-spectrum response spanning from visible to infrared light, which reveals a peak responsivity of 31.47 A/W and an ultrafast response time of 190/240 µs under 5 V bias and 810 nm illumination. In photoelectric synapse mode, the synapses exhibit tunable and stable synaptic plasticity under 365 nm illumination. Consequently, the synapses' multi-functionality is demonstrated through applications in both dual-band encrypted light communication and handwritten digit image recognition, achieving an accuracy of 89.12%.