A comparative study of the ZnO Fibers-based photodetectors on n-Si and p-Si

Abstract

The ZnO fibers (Fs)/p-Si (labeled D1) and ZnO Fs/n-Si (labeled D2) photodetector heterojunctions were fabricated and both devices gave a clear rectifying I–V characteristic with a high rectifying ratio, in the dark. At zero bias, D1 showed self-driven characteristics, while D2 had not and D1 was found to be more stable than D2 in time-dependent measurements. Optoelectronics results revealed that D1 had high sensitivity to both visible and excellent stability after 20 days. At zero bias, the ON/OFF ratio of the D1 photodetector was as high as 33 650 and in the dark, a rectification ratio of 67 400 within ±2 V was obtained for the D1 device. The maximum responsivities of the devices was ∼0.8 mA W−1, and their detectivity was ∼109 Jones. Furthermore, the ZnO Fs/p-Si (labeled D3) and ZnO Fs/n-Si (labeled D3) photodetectors yielded excellent response to 365 nm and 395 nm UV light (10 mW cm−2). Responsivity, detectivity (D), and external quantum efficiency values reached as high as 5.28 A W−1, 1.02 × 1013 Jones, and %16.6, respectively under 365 nm UV light. The excellent responses of the photodetectors to visible and UV light were attributed to the oxygen vacancies in ZnO and the formation of electron–hole pairs by the light effect and their separation by the electric field in the device formed between ZnO and Si.