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

• Published in: physica status solidi (b) Vol. 261; no. 7
• Main Authors: Uno, Kazuyuki, Yamaoka, Keishi
• Format: Journal Article
• Language: English
• Published: 01.07.2024
• Subjects: gallium oxides; mist chemical vapor depositions; photoconductivities; solar blind photodetectors; UV‐C photodetectors
• ISSN: 0370-1972; 1521-3951
• DOI: 10.1002/pssb.202300463

α‐Ga2O3 is a suitable material for UV‐C optical devices owing to its optical absorption edge wavelength. In this study, α‐Ga2O3 thin films are grown on c‐, a‐, m‐, n‐, and r‐oriented sapphire substrates by mist chemical vapor deposition. Furthermore, their structural fluctuations, Δω$\Delta \omega$ (normal direction of the surface) and Δϕ$\Delta \phi$ (rotational direction on the surface), are examined. As a result, the a‐oriented α‐Ga2O3 thin films exhibit the smallest Δω$\Delta \omega$ and Δϕ$\Delta \phi$. Based on the results of the previous examination, metal–semiconductor–metal (MSM) photodetectors are fabricated using c‐ and a‐oriented α‐Ga2O3 thin films and their photoconducting properties are characterized. Under D2 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 104.9$\left(10\right)^{4.9}$ at 10 V and 105.2 at 24 V. The photoresponsivity is estimated to be 2.2 A W−1 under the illumination of a D2 UV lamp and 24 V bias voltage. In these results, it is suggested that the a‐oriented α‐Ga2O3 thin film exhibits a higher in‐plane carrier mobility than the c‐oriented film. Thus, a‐oriented α‐Ga2O3 films are more suitable than c‐oriented α‐Ga2O3 films for fabricating MSM photodetectors. Metal–semiconductor–metal (MSM) photodetectors are fabricated by mist chemical vapor deposition growth of α‐Ga2O3 on c‐ and a‐oriented sapphire substrates. The MSM photodetector using a‐oriented α‐Ga2O3 thin films produces greater photoconductivity than that using c‐oriented films, and exhibits the ultraviolet–visible‐light rejection ratio of 105.2 at 24 V and the photoresponsivity 2.4 A W−1