Improvement of Photoconductivity in a‐Oriented α‐Ga₂O₃ Thin Films Grown on Sapphire Substrates by Mist Chemical Vapor Deposition

α ‐Ga 2 O 3 is a suitable material for UV‐C optical devices owing to its optical absorption edge wavelength. In this study, α ‐Ga 2 O 3 thin films are grown on c‐, a‐, m‐, n‐, and r‐oriented sapphire substrates by mist chemical vapor deposition. Furthermore, their structural fluctuations, (normal direction of the surface) and (rotational direction on the surface), are examined. As a result, the a‐oriented α ‐Ga 2 O 3 thin films exhibit the smallest and . Based on the results of the previous examination, metal–semiconductor–metal (MSM) photodetectors are fabricated using c‐ and a‐oriented α ‐Ga 2 O 3 thin films and their photoconducting properties are characterized. Under D 2 lamp light illumination, the MSM photodetector using a‐oriented films produces photocurrent four to six times greater than those using c‐oriented films. The visible‐light rejection ratios are at 10 V and 10 5.2 at 24 V. The photoresponsivity is estimated to be 2.2 A W −1 under the illumination of a D 2 UV lamp and 24 V bias voltage. In these results, it is suggested that the a‐oriented α ‐Ga 2 O 3 thin film exhibits a higher in‐plane carrier mobility than the c‐oriented film. Thus, a‐oriented α ‐Ga 2 O 3 films are more suitable than c‐oriented α ‐Ga 2 O 3 films for fabricating MSM photodetectors.