Microstructures and Optical Properties of Ga₂O₃ Coatings Synthesized by Magnetron Sputtering at Room Temperature

The Ga₂O₃ thin films were synthesized by RF magnetron sputtering at room temperature on substrates of Si-wafer and quartz-glass.The influence of the Ar/O₂ flow-rate ratio and annealing temperature on the microstructures and optical properties of “cold-deposited” Ga₂O₃ coatings was investigated.The results show that an O₂-addition and post-annealing significantly improved the microstructures and optical properties of the conventional hot-deposited Ga₂O₃ coatings.For example,cold-deposited at 175 W and Ar/O₂ flow-rate ratio of 80∶20,the 197.6 nm thick Ga₂O₃ coatings,annealed at 900℃,had an absorption peak at 284 nm in ultraviolet band,a transmittance peak of 92.82%,and a resistivity of 137.21 m·cm.As the annealing temperature increased from 700℃ to 1000℃,the optical band-gap decreased from 5.28 to 4.93 eV,and the preferential growth of β-Ga₂O₃ grains,in <201>,<401> and <403> orientations,became increasingly pronounced.