Te 0.75 Se 0.25 /Si/AZO Dual‐Heterostructure Photodetector for Spectral Selective Imaging and Secure Optical Communication

Abstract Multispectral photodetectors (PDs) enable simultaneous photon detection across distinct bands, unlocking advanced capabilities such as precision object identification, autonomous navigation, and secure optical communication through spectral‐specific signal discrimination. However, the integration of multiple spectral detection functionalities into a single device architecture remains a challenge. Here, a two‐terminal, vertically stacked dual‐heterostructure (DH) photodetector composed of a Te 0.75 Se 0.25 /Si/AZO (P‐N‐N + ) configuration that achieves broadband spectral detection (300–1750 nm) under zero‐bias operation while exhibiting a tunable bipolar photoresponse is presented. The device demonstrates high‐performance metrics, including a specific detectivity exceeding 10 11 Jones, a −3 dB cutoff frequency of 280 kHz, and an ultrafast response time of 726 ns under 1550 nm illumination. The selective detection of visible (VIS) and short‐wave infrared (SWIR) spectra is effectively adjusted by varying the applied bias voltage. Capitalizing on these rapid response and bipolar characteristics, this PD facilitates pixel‐level imaging and secure optical communication with encryption capability. Furthermore, a scanning imaging system that operates without the removal of an infrared cut‐filter, achieving high‐quality image recognition with a grayscale resolution beyond a 9‐level grayscale is demonstrated. This work provides a promising strategy for developing bias‐switchable, multimodal photodetectors with diverse applications in advanced imaging and communication technologies.