Influences of Process Temperature on a Phase of Ga2O3 Thin Films Grown by Atomic Layer Deposition on Sapphire

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Influences of process temperature on the phase of Ga2O3 thin films grown by atomic layer deposition (ALD) on a sapphire substrate is investigated. Ga2O3 thin films grown by ALD at a process temperature of 200°C showed an amorphous phase; however, crystalline α‐Ga2O3 film was deposited at the deposition temperatures from 225 to 250°C. Above a process temperature of 300°C, α and β phases coexist in the grown Ga2O3 thin film. Interestingly, β‐Ga2O3 thin film was deposited on the sapphire by an increase of working pressure during Ga2O3 ALD process at the process temperature of 300°C. The bandgap of β‐Ga2O3 thin film was as high as ~5.2 eV. A metal–semiconductor–metal type photodetector using the β‐Ga2O3 thin film exhibited a fast response speed with a short rise time of 1.3 μs for the detection of deep ultraviolet wavelengths.