Tunable p-type doping of Si nanostructures for near infrared light photodetector application

Abstract

In this study, we present a simple oxide assisted p-type doping of Si nanostructures by evaporating a mixed powder composed of SiB₆ and SiO. It was found that Si nanoribbons (Si NRs) which can be obtained at high SiB₆ content, will give way to Si nanowires (Si NWs) when the content of SiB₆ in the mixed powder was reduced. According to our transport measurement of field effect transistors (FETs) assembled on individual Si nanostructures, the as-prepared Si nanostructures with different boron doping levels all exhibit typical p-type conduction characteristics. Additionally, the electrical conductivity of the Si nanostructures can be tuned over 7 orders of magnitude from 8.98 × 10² S cm⁻¹ for the highly doped sample to 3.36 × 10⁻⁵ S cm⁻¹ for the lightly doped sample. We also assembled a nano-photodetector based on monolayer graphene and the as-prepared Si nanostructures, which exhibits ultra-sensitivity to 850 nm near infrared light (NIR) illumination with a nanosecond response speed (τ_rise/τ_fall: 181/233 ns). The generality of the above results suggest that the Si nanostructures are promising building blocks for future electronic and optoelectronic device applications.