Effects of morphology and doping on the electronic and structural properties of hydrogenated silicon nanowires

We study the electronic and atomic structures of hydrogenated silicon nanowires (SiNWs) by changing the mean diameter, morphology, and orientation using state-of-the-art density functional calculations. Most of the SiNWs are found to have large and direct band gaps, which make them very interesting for silicon-based nano-optoelectronic devices and lasers. The band gap increases with decreasing diameter in all cases because of quantum confinement, but the scaling is dependent on the morphology of the SiNWs. For thin [112] SiNW, the calculated band gap agrees well with the recent experiments. Variation in hydrogen concentration is used to explore the sensing capabilities of different surface morphologies and the associated surface reconstructions. Further studies on p- or n-doping show bulklike modifications in the electronic structure with several advantages that can be used to design nanoscale devices of SiNWs.