Effect of thickness on the performance of solar blind photodetectors fabricated using PLD grown β-Ga2O3 thin films

Herein, we are reporting the fabrication of high-performance solar blind photodetectors using beta-Ga2O3 thin films of varying thicknesses grown on single crystal (0001) Sapphire substrate by pulsed laser deposition (PLD) technique. Thickness of the beta-Ga2O3 films was varied by varying the number of ablating laser shots from 1000 to 15,000 (1 k to 15 k). The effect of thickness on the structure, surface morphology and optical properties of the films was investigated using several state-of-the-art techniques such as X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM) and ultraviolet-visible (UV-Vis) spectroscopy. All the films were found to be made of phase-pure beta-Ga2O3 with high crystal quality. The orientation of the films was found to gradually change from (-201) to (-201)/(400) as the number of laser shots increased from 1 k to 15 k. The bandgap of the films made with 1 k laser shots was found to be 5.26 eV which decreased monotonously with increase in number of laser shots and became 4.79 eV for the films made with 15 k laser shots. The detailed time-resolved photoresponse measurements showed that the films made with 2 k shots exhibit the best photoresponse characteristic among all the films with a high I-photo/I-dark ratio of similar to 6.7 x 10(4) and short rise (0.38 mu s) and decay times (142 mu s). Our results indicate that the PLD-grown beta-Ga2O3 thin films, with optimized thickness, can play a major role in next-generation solar-blind ultraviolet photodetector technology. (C) 2019 Published by Elsevier B.V.