Vertical Black Phosphorus Photodiodes with High Quantum Efficiency for Mid‐Infrared Detection at Room Temperature

Abstract Infrared (IR) photodetectors play a crucial role in various fields such as medical imaging, communication, and surveillance. However, the majority of commercial infrared detectors require low‐temperature operation, which limits their broader applications. Recently, room temperature infrared photodetectors based on 2D materials have shown potential for expanding their use, yet their performance is often constrained by low quantum efficiency. In this study, a vertical black phosphorus (BP) Schottky photodiode designed for room temperature mid‐IR photodetection with enhanced quantum efficiency is reported. By optimizing both optical and electrical aspects of the design, near‐perfect absorption is achieved through a resonant cavity and improve carrier separation and collection efficiency via Schottky and ohmic contacts, respectively. The photodetector demonstrates high sensitivity, with a specific detectivity of 2.2 × 10⁹ cm Hz^1/2 W⁻¹, and a maximal external quantum efficiency of 42% at 3.6 µm. Additionally, due to BP's intrinsic anisotropic absorption, the device exhibits an exceptionally high polarization sensitivity with a polarization ratio of 10 and a polarization angle sensitivity of 0.01 A W⁻¹ degree⁻¹ is achieved at 3.8 µm. This device design provides a promising approach for high‐performance, room‐temperature infrared photodetectors, combining low power consumption with polarization imaging capabilities.