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-Ga₂O₃ films grown on α-Al₂O₃ (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-Ga₂O₃ ( \(\stackrel{-}{2}\) $\stackrel{-}{2}$ 01) ∥α-Al₂O₃ (0001) and β-Ga₂O₃ [010] ∥α-Al₂O₃ < \(\stackrel{-}{1}\) $\stackrel{-}{1}$ 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.