High-Performance Self-Powered Vertical MoTe₂ p-i-n Photodiode for Near-Infrared Detection and Spike Encoding

High-performance near-infrared (NIR) photodetectors are essential for advanced technologies such as industrial sorting, light detection and ranging (LiDAR), and biomedical imaging. Silicon-based devices face a significant decrease in the light absorption coefficient beyond 0.9 μm, where the thick active layer required for sufficient light absorption leads to a trade-off between performance and power consumption. Here, we report a high-performance, self-powered vertical p-type/intrinsic/n-type (p-i-n) photodiode based on a van der Waals WSe₂/MoTe₂ heterostructure for near-infrared detection. By engineering band alignment and heavy doping, the photodiode establishes a robust vertical built-in electric field to facilitate efficient carrier separation and achieves low series resistance for effective carrier collection. At 1064 nm, the photodiode exhibits a high responsivity of 787 mA·W^-1, an external quantum efficiency (EQE) of 91.7%, and a fast impulse response time (19.5 ns) under zero voltage bias. Furthermore, the integration of p-i-n photodiode with a voltage-controlled oscillator demonstrates a bioinspired optical-to-electrical spike conversion mechanism. This functional similarity to the signal encoding of retinal ganglion cells highlights a feasible hardware pathway for neuromorphic vision applications.