Simplified chemical processed Cd1−x Al x S thin films for high-performance photodetector applications

Abstract

Abstract In this present investigation, we report the effect of aluminum (Al) doping on the photoelectric performance of cadmium sulfide (CdS) thin films prepared by cost-effective automatic nebulizer spray method. The doping of Al concentrations varied from 1 at.% to 9 at.% in the steps of 3 at.%. X-ray diffraction (XRD) patterns show hexagonal crystal structure with polycrystalline nature and the enrichment of crystallite sizes as a function of Al doping concentrations. The formed impurity phase i.e. CdO might be helpful in enhancing the photoelectric performance by its additional photo-generated charge carriers. The optical studies confirm the maximum absorption showed in the visible spectral range with the corresponding minimum bandgap of 2.28 eV for 6 at.% of Al. The room temperature photoluminescence studies show an increase of near-band-edge (NBE) emission as a function of Al doping concentration and this NBE is close to the obtained bandgap in terms of wavelength. In addition, the observed red emission at 635 nm is due to the surface-related impurities or native defect states. From the present work, the observed responsivity (R), external quantum efficiency (EQE) and detectivity (D*) of the CdS:Al detectors are 8.64 AW−1, ∼2018% and 9.29 × 1011 jones, respectively for the optimum 6 at.% of CdS:Al film. The performance of CdS:Al films reported in this work are significantly improved when compared with literature reports. The present investigation, therefore offers a potential material, CdS:Al, as a photodetector for various scientific and industrial applications.