Ex situ vapor phase boron doping of siliconnanowires using BBr3

Abstract

An ex situ vapor phase technique for doping vapor–liquid–solid grown silicon nanowires (NWs) based on the reduction of BBr₃ by H₂ has been demonstrated. Electron microscope images show that the excellent crystal quality of the nanowires is preserved with minimal alteration of their surface morphology. Fano resonance in the Raman spectra for single nanowires indicates that active boron concentrations over two orders of magnitude and as high as 10²⁰ cm⁻³ are achievable in a well-controlled manner, with excellent axial uniformity. Electrical resistance measurements from single nanowires confirm that incorporated boron is electrically active, and doping of epitaxial bridging Si NWs is successfully demonstrated. By avoiding the pitfalls of nonuniform concentration profiles and drastic morphological changes that often accompany in situ boron doping, this technique provides a valuable alternative doping route for the development of single Si NW devices in a reliable manner.