Effect of Arsenic Depletion on the Silicon Doping of Vapor-Liquid-Solid GaAs Nanowires

It is well known that chemical potential driving the vapor-liquid-solid growth of nanowires oscillates in synchronization with the monolayer growth. In III-V nanowires, this occurs due to depletion of group V atoms in a catalyst droplet. The amphoteric behavior of silicon doping, which often changes from n-type in planar GaAs layers to p-type in nanowires, is attributed to low arsenic concentrations. Herein, we present an analytical model which quantifies the doping oscillations over the monolayer formation cycle, and its impact on the electron-to-hole ratio for the silicon doping of GaAs nanowires. It is shown that arsenic depletion can easily double the amphoteric effect and strongly favor the tendency for p-type doping. On a more general ground, the nanowire doping process appears highly sensitive to the chemical potential oscillations related to a restricted amount of material in a nanoscale catalyst.