Gallium Nitride (GaN) Nanostructures and Their Gas Sensing Properties: A Review

Abstract

In the last two decades, GaN nanostructures of various forms like nanowires (NWs), nanotubes (NTs), nanofibers (NFs), nanoparticles (NPs) and nanonetworks (NNs) have been reported for gas sensing applications. In this paper, we have reviewed our group’s work and the works published by other groups on the advances in GaN nanostructures-based sensors for detection of gases such as hydrogen (H2), alcohols (R-OH), methane (CH4), benzene and its derivatives, nitric oxide (NO), nitrogen dioxide (NO2), sulfur-dioxide (SO2), ammonia (NH3), hydrogen sulfide (H2S) and carbon dioxide (CO2). The important sensing performance parameters like limit of detection, response/recovery time and operating temperature for different type of sensors have been summarized and tabulated to provide a thorough performance comparison. A novel metric, the product of response time and limit of detection, has been established, to quantify and compare the overall sensing performance of GaN nanostructure-based devices reported so far. According to this metric, it was found that the InGaN/GaN NW-based sensor exhibits superior overall sensing performance for H2 gas sensing, whereas the GaN/(TiO2–Pt) nanowire-nanoclusters (NWNCs)-based sensor is better for ethanol sensing. The GaN/TiO2 NWNC-based sensor is also well suited for TNT sensing. This paper has also reviewed density-functional theory (DFT)-based first principle studies on the interaction between gas molecules and GaN. The implementation of machine learning algorithms on GaN nanostructured sensors and sensor array has been analyzed as well. Finally, gas sensing mechanism on GaN nanostructure-based sensors at room temperature has been discussed.

Morphology of Ga2O3 Nanowires and Their Sensitivity to Volatile Organic Compounds

“…If the radius of the nanowire is larger than the effective Debye length, the surface plays an important role in the process of transport of an electric charge. Whereas if the radius of the nanowire is smaller than the Debye length, electrons from the volume become bound to oxygen chemisorbed at the surface, and then the conductance is determined by the volume of the nanowires [ 53 , 54 ].…”

Emerging MXene–Polymer Hybrid Nanocomposites for High-Performance Ammonia Sensing and Monitoring

“…Various NH 3 detecting techniques ( Figure 2 ) include calorimetric, gravimetric, electrochemical, optical, chromatographic, laser-based, catalytic, resistive, acoustic, and quartz crystal microbalance-based methods [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ]. Among them, chemiresistors have become critical NH 3 sensing technologies due to their miniaturized design, low-cost, user-friendly, portable, and energy efficiency to detect NH 3 (at ~1ppb) in human breath, workplace leak, and agricultural fields [ 10 , 13 ].…”

“…Currently, 2D sensing nanomaterials owing to their larger specific surface area, tunable chemistries, and their fabrication techniques, have been extensively studied in terms of three S’s (sensitivity, selectivity, and stability) and five essential R’s (room temperature operation, range of detection, repeatability, response and recovery, and reproducibility) [ 11 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. A 2D material (such as graphene and its derivatives, 2D organic frameworks, and polymers, black phosphorus, borophene, metal dichalcogenides, phosphorene, molybdenum disulfide, metal carbides, or nitrides (MXenes)) is generally stated to an atomically thin layer or few layers of flakes with thickness varying from 1–5 nm [ 14 , 21 ].…”

“…MXene–polymer nanocomposites have recently aroused inordinate interest in NH 3 sensing applications. However, there are reports on nanocomposites of polymers with other 2D materials such as graphene and its derivatives, metal dichalcogenides and molybdenum disulfide [ 11 , 14 , 17 , 18 , 19 , 20 ]. However, the fabrication and functionalization of such nanocomposites is tedious, which limits their application in ammonia monitoring [ 11 , 14 , 17 , 18 , 19 , 20 ].…”

Back-Gate GaN Nanowire-Based FET Device for Enhancing Gas Selectivity at Room Temperature

“…Nanowires exhibit one-dimensional nanostructures that offer large surface-to-volume ratio, suitable for gas-sensing applications [ 9 , 10 ]. In the past few years, several nanowire-based gas sensors have been reported showing enhanced sensing performance in comparison to their bulk counterpart [ 11 , 12 , 13 ].…”