Fabrication and characterization of efficient visible-NIR CdS/porous Si/p-Si photodetectors via laser-enhanced chemical bath deposition

Abstract

The progress in preparation techniques of semiconducting thin film is a fundamental aspect of present-day electronics, addressing the increasing need for high-efficiency and cost-effective optoelectronic devices. The CdS-porous silicon (PSi) heterostructure has drawn significant attention for advanced technological and industrial applications, such as solar cells and photodetectors. Nevertheless, conventional chemical bath deposition (CBD) commonly produces CdS films with limited crystallinity, high defect density, and non-uniform morphology, which reduce device performance. Therefore, developing a simple, cost-effective technique to improve the structural quality of CdS without modifying the chemical route is highly desirable. This study presents a method that uses green diode laser illumination to improve the quality of the CdS films prepared by the CBD process. X-ray diffraction XRD investigations of the CdS film prepared with laser illumination reveal improved crystallinity compared with the as-deposited CdS film. Optical absorption measurements show that the optical energy gap of the CdS film increases from 2.38 eV to 2.61 eV when laser illumination is employed during film deposition. Scanning electron microscopy (SEM) studies confirm a reduction in the agglomeration of CdS particles when subjected to laser illumination, with the CdS particles being effectively incorporated inside the pores of PSi. The CdS-embedded PSi photodetector shows an increase in responsivity from 1.9 to 4.5 A W⁻¹ at 480 nm when laser illumination is applied during deposition. Additionally, the rise and fall times of the photodetector fabricated with laser illumination are 159 ms and 208 ms, respectively. The results indicate improved spectral response and external quantum efficiency (EQE), enhanced detection capability, and reduced noise equivalent power (NEP), signifying greater device sensitivity to laser light.