Effects of film thickness on crystal structure, surface topography, optical, and photoelectric properties of Ga₂O₃ thin film based solar blind photodetectors

beta-Ga2O3 epitaxial thin films with different thicknesses were grown on Al2O3 (0001) substrates by the pulse laser deposition technology. The full width at half maximum of XRD rocking curve, grain size, surface roughness, and optical absorbance (200-300 nm) of the beta-Ga2O3 films increase with increasing film thickness. In addition, with increasing film thickness, the adsorption edge presents a red-shift phenomenon, which is accompanied by a slight decrease in the optical band gap ( E-g ). The metal-semiconductor-metal type photodetector made with the 401-nm beta-Ga2O3 film shows the maximal photocurrent (1.06 mu A @ 10 V), photo-to-dark current ratio (6.96 x 10(4)), responsivity (90 mA W-1), and detectivity (0.5 x 1011 Jones) under 254-nm UV light illumination with a light intensity of 98.4 mu W/cm(2). Moreover, the 401-nm photodetector displays a small rise time of 0.111/0.561 s and a decay time of 0.046/0.047 s as well as a good stability and repeatability. These findings provide useful reference for the fabrication of beta-Ga2O3 film based solar blind ultraviolet photodetectors.