Effect of trimethylgallium flow rate on structural and photoelectronic properties of β-Ga2O3 films prepared by MOVPE

This study investigated the effect of trimethylgallium flow rate on the structural and photoelectronic properties of β -Ga 2 O 3 films grown on α -Al 2 O 3 (0001) substrates using MOVPE method. As the source flow rate gradually decreased from 7.2 mol/min to 3.6 mol/min, the films gradually changes from polycrystalline to a single epitaxial orientation, and the epitaxial relationships between the film and the substrate were β -Ga 2 O 3 ( 2 - 01) ∥ α -Al 2 O 3 (0001) and β -Ga 2 O 3 [010] ∥ α -Al 2 O 3 < 1 - 010>. The film thickness was reduced from 767.4 to 329.2 nm and the surface root-mean-square roughness decreased from 18.1 to 5.84 nm. The average transmittance in the visible range increased from 81.2 to 83.4%, and the optical bandgap width increased from 4.80 to 4.95 eV. The prepared MSM-structured photodetectors (PDs) could continuously switch response to 254 nm UV light, and the PD prepared at 7.2 mol/min source flow rate had a maximum photo current of 1405.2 nA. However, the PD prepared under the condition of 3.6 mol/min had the lowest dark current, the highest photo-dark current ratio, shorter fast response time, and a good retention characteristic.