Bidirectional Photoresponse in a Mixed-Dimensional MoS<sub>2</sub>/Ge Heterostructure and Its Optic-Neural Synaptic Behavior for Colored Pattern Recognition
Yichi Zhang, Bo Wang, Han Zhao, Xinlong Shi, Ningning Zhang, Tian Miao, Dongdong Lin, Zuimin Jiang, Maliang Liu, Hui Guo, Jincheng Zhang, Huiyong Hu, Liming Wang
Abstract
Realization of multi-functional synaptic devices is imperative to deploy high-performance brain-like vision systems. Here, a junction field-effect transistor based on a two-dimensional MoS 2 /three-dimensional Ge heterojunction structure is presented. The heterojunction gate ensures efficient electrostatic gate control and eliminates hysteresis, which highlights its capability for high-performance electronic circuit applications. With the visible absorptive MoS 2 channel and the infrared absorptive Ge gate, a positive photoresponse to visible light and a negative photoresponse to infrared light are obtained simultaneously. Responsivities reach as high as 24.9 and −0.40 A/W at 532 and 1550 nm, corresponding to a detectivity of 7.9 × 10 11 and −1.3 × 10 10 Jones. Meanwhile, based on its optical stimulation-controlled synaptic behaviors, an optoelectronic neural network for colored digit pattern recognition is developed. The recognition accuracy reaches as high as 89.6 and 91.6% for visible and near-infrared patterns, respectively. These results demonstrate a new pathway for realizing novel multi-wavelength neuromorphic visual systems.