Determination of Surface Depletion Thickness of p-doped Silicon Nanowires Synthesized Using Metal Catalyzed CVD Process

An in-depth understanding of the distribution and impact of doping in nanowires is crucial for the rational design of future nanowire based devices synthesized using bottom-up techniques. We used a very slow wet chemical etchant for progressive reduction of the diameters of boron-doped, metal-catalyzed silicon nanowires with diverse diameters and lengths. The low temperature process helped avert the dopant segregation which is common in high temperature processes such as oxidation for diameter reduction. We ensured identical surface conditions subsequent to diameter reduction with wet-chemical etching and, using DC current-voltage measurements, found the resistance to increase with decreasing diameter. As the diameters were shrunk from a larger diameter to ∼50 nm in diameter, they exhibited a strong non-linear increase of the resistance indicating complete depletion of the cross-section caused by surface charges. The dopant concentration of the nanowires was calculated to be 2.1×10
¹⁸
cm
^-3
and the corresponding surface charge density was around 2.6×10
¹²
cm
^-2
.