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

Abstract β -Ga 2 O 3 epitaxial thin films with different thicknesses were grown on Al 2 O 3 (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 β -Ga 2 O 3 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 β -Ga 2 O 3 film shows the maximal photocurrent (1.06 μ A @ 10 V), photo-to-dark current ratio (6.96 × 10 4 ), responsivity (90 mA W −1 ), and detectivity (0.5 × 10 11 Jones) under 254-nm UV light illumination with a light intensity of 98.4 μ 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 β -Ga 2 O 3 film based solar blind ultraviolet photodetectors.