A Review on Gallium Oxide Materials from Solution Processes

Abstract

Gallium oxide (Ga2O3) materials can be fabricated via various methods or processes. It is often mentioned that it possesses different polymorphs (α-, β-, γ-, δ- and ε-Ga2O3) and excellent physical and chemical properties. The basic properties, crystalline structure, band gap, density of states, and other properties of Ga2O3 will be discussed in this article. This article extensively discusses synthesis of pure Ga2O3, co-doped Ga2O3 and Ga2O3-metal oxide composite and Ga2O3/metal oxide heterostructure nanomaterials via solution-based methods mainly sol-gel, hydrothermal, chemical bath methods, solvothermal, forced hydrolysis, reflux condensation, and electrochemical deposition methods. The influence of the type of precursor solution and the synthesis conditions on the morphology, size, and properties of final products is thoroughly described. Furthermore, the applications of Ga2O3 will be introduced and discussed from these solution processes, such as deep ultraviolet photodetector, gas sensors, pH sensors, photocatalytic and photodegradation, and other applications. In addition, research progress and future outlook are identified.

Chemical Bath Deposition of α-GaOOH with Tunable Morphology on Silicon Using the pH Adjustment

“…17 The growth of β-Ga 2 O 3 thin films and nanostructures relies on a double-step process, consisting of initially forming Ga(III) oxide− hydroxide (GaOOH) thin films and nanostructures using CBD and subsequently converting them into β-Ga 2 O 3 thin films and nanostructures using thermal annealing at high temperature in air. 16 The first step using CBD basically governs the shape and size of the resulting nanostructures, while the second step using thermal annealing controls their crystalline phase. By using that double-step process, a large number of nanostructures with different shapes and sizes has been formed using the homogeneous growth in bulk solution.…”

“…9 Alternatively, several chemical deposition techniques in solution have been developed to grow β-Ga 2 O 3 thin films and nanostructures, including sol−gel process, hydrothermal synthesis, and chemical bath deposition (CBD). 10−15 The CBD process using gallium nitrate (Ga(NO 3 ) 3 ) in an aqueous solution and working at low temperature (<100 °C) and at atmospheric pressure is considered a low-cost, surface-scalable, and easily implemented process, 16 which is in line with the development of green chemistry. 17 The growth of β-Ga 2 O 3 thin films and nanostructures relies on a double-step process, consisting of initially forming Ga(III) oxide− hydroxide (GaOOH) thin films and nanostructures using CBD and subsequently converting them into β-Ga 2 O 3 thin films and nanostructures using thermal annealing at high temperature in air.…”

“…The CBD process using gallium nitrate (Ga­(NO 3 ) 3 ) in an aqueous solution and working at low temperature (<100 °C) and at atmospheric pressure is considered a low-cost, surface-scalable, and easily implemented process, which is in line with the development of green chemistry . The growth of β-Ga 2 O 3 thin films and nanostructures relies on a double-step process, consisting of initially forming Ga­(III) oxide–hydroxide (GaOOH) thin films and nanostructures using CBD and subsequently converting them into β-Ga 2 O 3 thin films and nanostructures using thermal annealing at high temperature in air . The first step using CBD basically governs the shape and size of the resulting nanostructures, while the second step using thermal annealing controls their crystalline phase.…”

Synthesis and Characterization of a Porous Ga2O3 Material with a Low Dielectric Constant

“…Considering all the requirements and combining the necessary factors, synthesis of the new candidate porous Ga etc. 14,15 The monoclinic β phase of gallium oxide (β-Ga 2 O 3 ) with lattice parameters: a = 12.2 Å, b = 3.0 Å, c = 5.8 Å, 16 stands out as the most thermally stable crystal structure when compared to other gallium oxide phases, namely, α-Ga 2 O 3 , γ-…”

“…Gallium oxide (Ga 2 O 3 ) is a wide-band-gap (4.8–4.9 eV) ceramic material with potential applications in power electronics, optoelectronics, electroluminescence devices, etc. , The monoclinic β phase of gallium oxide (β-Ga 2 O 3 ) with lattice parameters: a = 12.2 Å, b = 3.0 Å, c = 5.8 Å, stands out as the most thermally stable crystal structure when compared to other gallium oxide phases, namely, α-Ga 2 O 3 , γ-Ga 2 O 3 , δ-Ga 2 O 3 , and ε-Ga 2 O 3 . Remarkably, all these various gallium oxide phases can be converted to the final β phase under certain conditions .…”