Binary Multifunctional Ultrabroadband Self‐Powered g‐C₃N₄/Si Heterojunction High‐Performance Photodetector

Abstract Compact optical detectors with fast binary photoswitching over a broad range of wavelength are essential as an interconnect for any light‐based parallel, real‐time computing. Despite of the tremendous technological advancements yet there is no such single device available that meets the specifications. Here a multifunctional self‐powered high‐speed ultrabroadband (250–1650 nm) photodetector is reported based on graphitic carbon‐nitride (g‐C₃N₄)/Si hybrid 2D/3D structure. The device shows a novel binary photoswitching (change in current from positive to negative) in response to OFF/ON light illumination at small forward bias (≤0.1 V) covering 250–1350 nm. At zero bias, the device displays an extremely high ON/OFF ratio of ≈1.2 × 10⁵ under 680 nm (49 µW cm⁻²) illumination. The device also shows an ultrasensitive behavior over the entire operating range at low light illuminations, with highest responsivity (1.2 A W⁻¹), detectivity (2.8 × 10¹⁴ Jones), and external quantum efficiency (213%) at 680 nm. The response and recovery speeds are typically 0.23 and 0.60 ms, respectively, under 288 Hz light switching frequency. Dramatically improved performance of the device is attributed to the heterojunctions formed by the ultrathin g‐C₃N₄ nanosheets embedded in the Si surface.