Multifunctional Plasmonic Sensor for Excellent UV Photodetection and NO2 Gas Sensing by an Array of Al Nanocaps on GaN Truncated Nanocones

Plasmonics has been demonstrated to improve the performance of various optoelectronic devices operating in the infrared to visible wavelength regime. However, limited by optical properties of suitable plasmonic materials in ultraviolet (UV) regimes, rare works have been devoted to UV applications with plasmonic structures. This work deliberately fabricates a heterogeneous array of Al nanocaps (Al‐NC) on a wide‐bandgap semiconductor of GaN truncated nanocones (GaN‐TNC) and then presents a multifunctional plasmonic sensor for excellent UV photodetection and air‐quality‐index (AQI) gas sensing. As a UV photodetector, this work shows maximum responsivity (1.8 × 108 AW−1) and detectivity (1.2 × 1018 Jones) at the resonance wavelength of 355 nm, which based on the current knowledge, is the highest detectivity among GaN‐based UV photodetectors. Such a UV photodetector also introduces a decent response of rise time (78.3 ms) and fall time (303.5 ms), respectively. As a gas sensor, this work detects a key AQI gas of NO2 and provides a superior response of 28% and a detection limit of 500 ppb, respectively. The applications of UV photodetection and gas sensing based on the device utilizing aluminum (Al) plasmonic and the large surface area gallium nitride truncated nanocone array are demonstrated. It shows superior properties (responsivity, detectivity, and response time) for detecting the UV illumination light. As a gas sensor, this device also presents remarkable characteristics (response and response time) compared to other works.