Ultrasensitive and Fast Gas Detection Based on Room‐Temperature Indium Arsenide Mid‐Wavelength Infrared Photodetectors

Abstract Combustible hydrocarbon gases, typified by methane, are invisible, odorless, and imperceptible, yet they pose significant hazards to human safety and the environment. Therefore, monitoring these gases is crucial in managing and mitigating potential hazards. Here, a gas sensing system is proposed based on the non‐dispersive infrared absorption spectroscopy (NDIR) technique. Its core component is a home‐built indium arsenide (InAs) semiconductor mid‐wavelength infrared photodetector. By material growth and device structure optimization (a peculiar potential barrier layer is designed to form a heterojunction and suppress diffusion carriers), the InAs‐based photodetectors show a low‐noise performance of 1.62 × 10⁻¹² A·Hz^−1/2 and a record high room‐temperature detectivity of 2.1 × 10¹⁰ cm·Hz^1/2·W⁻¹ with superior response speed of <40 ns. The sensing system, therefore, gains an ultra‐sensitive (<1 ppm) and fast (≈350 ms) gas detection capability of methane compared to current NDIR equipment. The method used in this study paves an avenue for designing ultrasensitive NDIR systems based on photovoltaic devices and provides a new paradigm for highly integrated gas sensing hardware.