Core–shell silicon nanowire array–Cu nanofilm Schottky junction for a sensitive self-powered near-infrared photodetector

Abstract

A highly sensitive near infrared light (NIR) photodetector was fabricated by coating a thin layer of Cu film onto a vertical n-type SiNW array through a solution based reduction reaction. The as-fabricated core–shell SiNW array/Cu Schottky junction exhibits an obvious rectifying behavior in the dark with a turn-on voltage of ∼0.5 V and a rectification ratio of about 10² at ±1.5 V. In addition, it shows a pronounced photovoltaic performance when illuminated by NIR light with a wavelength of 980 nm. Such photovoltaic characteristics can allow the device to detect NIR illumination without exterior power supply. Further device analysis reveals that the self-powered NIR photodetector is capable of monitoring ultrafast optical signals with a frequency as high as 30 kHz. What is more, the present device also has obvious advantages of high responsivity, detectivity, on/off ratio, and response speed. Further theoretical simulation reveals that the good device performance is associated with excellent optical and electrical properties of core–shell heterojunction geometry.