ANNEALING TIME EFFECT ON NANOSTRUCTUREDn-ZnO/p-SiHETEROJUNCTION PHOTODETECTOR PERFORMANCE

In this work,n-ZnO/p-Siheterojunction photodetectors were prepared by drop casting ofZnOnanoparticles (NPs) on single crystal p-type silicon substrates, followed by (15–60) min; step-annealing at 600∘C. Structural, electrical, and optical properties of theZnONPs films deposited on quartz substrates were studied as a function of annealing time. X-ray diffraction studies showed a polycrystalline, hexagonal wurtizte nanostructuredZnOwith preferential orientation along the (100) plane. Atomic force microscopy measurements showed an averageZnOgrain size within the range of 75.9 nm–99.9 nm with a corresponding root mean square (RMS) surface roughness between 0.51 nm–2.16 nm. Dark and under illumination current–voltage(I–V)characteristics of then-ZnO/p-Siheterojunction photodetectors showed an improving rectification ratio and a decreasing saturation current at longer annealing time with an ideality factor of 3 obtained at 60 min annealing time. Capacitance–voltage(C–V)characteristics of heterojunctions were investigated in order to estimate the built-in-voltage and junction type. The photodetectors, fabricated at optimum annealing time, exhibited good linearity characteristics. Maximum sensitivity was obtained whenZnO/Siheterojunctions were annealed at 60 min. Two peaks of response, located at 650 nm and 850 nm, were observed with sensitivities of 0.12–0.19 A/W and 0.18–0.39 A/W, respectively. Detectivity of the photodetectors as function of annealing time was estimated.