Lightly doped single crystalline porous Si nanowires with improved optical and electrical properties

Abstract

The doping level of Si is crucial for its optical and electrical properties, and only highly doped porous Si nanowires have been reported in recent studies. Herein, we demonstrate the fabrication of lightly doped single crystalline porous Si nanowire arrays through metal-assisted chemical etching from lightly doped n-type (100) Si wafers. In this process, though the etching temperature and concentration of H₂O₂ in the etchant have significant effects on the uniformity and density of the porosity of the Si nanowires, the forming porous Si nanowires is available without the use of H₂O₂ in the etchant, which is different from the previous cases of fabricating porous Si nanowires from a highly doped Si wafer. Importantly, as-fabricated lightly doped porous Si nanowire arrays possess improved optical and electrical properties: the current value range of individual porous Si nanowire is ∼3 times as large as that of an individual solid Si nanowire under the same applied voltages range, suggesting that porous Si nanowires have enhanced electrical conductivity; an intensive photoluminescence emission peak is centered at 560 nm, showing a blue-shift of 90–120 nm compared with those of highly doped Si nanowires. The results indicate that the lightly doped single crystalline porous Si nanowires may shed light on new opportunities for nanoscale optoelectronic devices, electronics, photo-catalytic substrates and sensors.