Surface depletion thickness of p-doped silicon nanowires grown using metal-catalysedchemical vapour deposition

Abstract

An accurate evaluation of the radial dopant profile in a nanowire is crucial for designingfuture nanoscale devices synthesized using bottom-up techniques. We developed a very slowwet chemical etchant for gradually reducing the diameters of metal-catalysed,boron-doped silicon nanowires with varying diameters and lengths. Particularcare has been taken to perform the experiment at room temperature to preventdopant segregation, which is common in high temperature processes. By ensuringidentical surface conditions subsequent to diameter reduction, the resistance of thenanowires was measured and, as anticipated, was found to increase with decreasingdiameter. As the diameters were shrunk using wet-chemical etching, nanowiresexhibited a non-linear increase of the resistance when the diameter was reduced to∼50 nm. This is an indication of near-complete depletion in the nanowires caused bynanowire surface charges. The dopant concentration of the nanowires was found to be2.1 × 1018 cm−3 and the corresponding surface charge density was around2.6 × 1012 cm−2.