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Ga2O3 has been a subject of interest in research field with varying applications for current and future generation electronic devices. Due to its ultra-wide bandgap of 4.5–5.0 eV, extremely high BFOM of 3444, and other prominent characteristics relating to material properties, easy to mass-produce and economical, β-Ga2O3 finds applications in variety of electronics devices, power devices and optoelectronics devices. A comprehensive review of RF sputtered β-Ga2O3 films along with its properties, studies and applications are presented in this paper for the first time. Polymorphs of gallium oxide and crystal structure are discussed. Structural and chemical composition studies are reviewed with XRD and XPS. This review summarizes the recent progress in effects of sputtering parameters on film properties of Ga2O3. This review provides an in-depth analysis of mechanical, optical, film morphology, electrical properties of RF sputtered β-Ga2O3 films. The role of sputtering parameters such as substrate temperature, sputtering power, annealing temperatures and oxygen composition in the reactive sputtering for crystallinity are discussed. Furthermore, doping elements effects on bandgap changes are reported.

In this research, CuGaO2 thin films were prepared on quartz substrates by a radio frequency magnetron sputtering technique at 400℃ followed by subsequent annealing in N2 ambience. The effects of annealing temperature on structural, morphological, optical, and electrical properties of CuGaO2 thin films is reported. X-ray Diffraction (XRD) analysis confirmed the presence of single phase CuGaO2 in the film annealed at 900℃. Near stoichiometric composition ratio of Cu:Ga (1:1.08) was identified in the film annealed at 900℃. Field emission scanning electron microscopy showed an increase in the grain size with increase in annealing temperature. A UV-Vis spectrophotometer was used to perform optical studies in the 200-800nm wavelength region on all films. The optical bandgap was calculated from the transmission studies and was found to be in the range of 2.77 to 3.43 eV. The films annealed at temperatures 800℃ and above were found to be p-type. The lowest resistivity value of 230 Ω-cm was achieved for the film annealed at 900℃.

A metal-oxide-semiconductor field-effect transistor (MOSFET) with transparent ZnO as its gate metal was fabricated and its photodetecting capabilities were investigated. For the fabrication of the MOSFET, a four level mask was used. The first level was used for making the diffusion wells for source and drain. The second level to form the via holes for Aluminum deposition followed by the third level to shape the source and drain contact structures. The ZnO gate metal was then deposited by sputtering process. Finally the fourth level mask was used to pattern the ZnO gate metal. The electrical characteristic analysis was performed on the fabricated MOSFETs when different types of light were incident on it.

The Cu 2 O thin films were synthesized by using RF sputtering technique. Comparisons were made with films created by deposition at room temperature followed by thermal annealing between 100˚C and 400˚C and using different gases, oxygen (O 2 ) (oxidizing and reactive gas) and nitrogen (N 2 ) (inert gas), besides air. The thickness of the thin films was kept constant, around 2000 Å (Angstrom). In addition, the RF power and pressure deposition were kept constant, as well. The thin films were evaluated for a range of wavelengths between 200 nm and 400 nm (Ultra Violet spectrum), 400 nm and 700 nm (Visible spectrum), 700 nm and 800 nm (Infrared spectrum) for both, optical transmittance and photoluminescence. From the experimental results, the higher annealing temperature and the introduction of nitrogen (N 2 ) gas produced the following results: the optical bandgap for the Cu 2 O was found to be 2.23 eV and photoluminescence peaks were around 551 nm and 555 nm, which matched the theoretical analyses. Overall, there was a decrease in the optical bandgap of the Cu 2 O from 2.56 eV at room temperature to 2.23 eV for the film annealed in nitrogen gas at 400˚C. This indicates that the Cu 2 O is a potential candidate in solar cell applications.