Gallium Oxide for Gas Sensor Applications: A Comprehensive Review

Abstract

Ga2O3 has emerged as a promising ultrawide bandgap semiconductor for numerous device applications owing to its excellent material properties. In this paper, we present a comprehensive review on major advances achieved over the past thirty years in the field of Ga2O3-based gas sensors. We begin with a brief introduction of the polymorphs and basic electric properties of Ga2O3. Next, we provide an overview of the typical preparation methods for the fabrication of Ga2O3-sensing material developed so far. Then, we will concentrate our discussion on the state-of-the-art Ga2O3-based gas sensor devices and put an emphasis on seven sophisticated strategies to improve their gas-sensing performance in terms of material engineering and device optimization. Finally, we give some concluding remarks and put forward some suggestions, including (i) construction of hybrid structures with two-dimensional materials and organic polymers, (ii) combination with density functional theoretical calculations and machine learning, and (iii) development of optical sensors using the characteristic optical spectra for the future development of novel Ga2O3-based gas sensors.

Artificial intelligence process control: deep reinforcement learning for Ga2O3 wafer production

“…Gallium oxide is also used for highly sensitive gas sensors [8] and can be used to make solar-blind ultraviolet photodetectors, which allow monitoring of the ozone hole and space communication. [9] Disadvantages of gallium oxide include its poor heat conductivity and its lack of p-type doping. The former issue can be ameliorated by using thin layers of gallium oxide and bonding wafers to heat sinks.…”

Electrical and Gas Sensor Properties of Nb(V) Doped Nanocrystalline β-Ga2O3

“…Another notion is that β-Ga 2 O 3 , either described in this study or in reports of other scholars, is better suited for VOCs detection rather than simple gases, such as hydrogen or methane. The reason is that the mechanism of sensor response relies on the mobility of lattice oxygen ions at the surface of β-Ga 2 O 3 grains, rather than chemisorbed oxygen species [16]. This mechanism requires stronger adsorption of reducing gas molecule, which is better fulfilled in case of bigger organic molecules with polar functional groups.…”

“…However, gallium oxide β-Ga 2 O 3 shows n-type semiconductor properties only at high temperatures due to band gap width about 4.9 eV, while exact value varies depending on material physical state [15]. As a result, thin gas sensing films of Ga 2 O 3 usually show their optimum performance towards either oxidizing or reducing gases, among which are O 2 , NO, O 3 , CO, CH 4 and other hydrocarbons, ammonia and volatile organic compounds, only at high temperatures over 450 • C [16]. Efforts to decrease operating temperatures of gallia-based gas sensors are directed at composite sensitive materials formation [17][18][19], decoration with noble metals, possessing catalytic properties [20,21] or exploitation of size effect of nanocrystalline high surface area Ga 2 O 3 -based materials [22][23][24].…”

Room-Temperature TiO2 Gas Sensor with Conical-TSV Using a Thermal Oxidation Process

“…Among these, MOS-based gas sensors have garnered significant attention due to their outstanding sensing capabilities, such as rapid response time, high selectivity, and stability . There has been a growing research interest in nanostructured MOS-based sensors, leveraging their unique physicochemical properties to detect NO2. − These sensors can be categorized into two types: n-type semiconductors, including ZnO, SnO 2 , WO 3 , TiO 2 , MoO 3 , Ga 2 O 3 , V 2 O 5 , and Fe 2 O 3 ; and p-type semiconductors, such as CuO, Co 3 O 4 , NiO, MoS 2 , Mn 3 O 4 , and Cr 2 O 3 …”