Correlated Chemical And Electrically Active Dopant Analysis In Catalyst-Free Si-Doped InAs Nanowires.

Direct correlations between dopant incorporation, distribution and their electrical activity in semiconductor nanowires (NW) are difficult to access and require a combination of advanced nanometrology methods. Here, we present a comprehensive investigation of the chemical and electrically active dopant concentrations in n-type Si-doped InAs nanowires (NW) grown by catalyst-free molecular beam epitaxy using a various complementary techniques. N-type carrier concentrations are determined by Seebeck effect measurements and four-terminal NW-field effect transistor characterization and compared with the Si dopant distribution analyzed by local electrode atom probe tomography. With increased dopant supply a distinct saturation of the free carrier concentration is observed in the mid-1018 cm-3 range. This behavior coincides with the actual Si dopant concentrations in the bulk part of the NW, suggesting the absence of compensation effects. Importantly, excess Si dopants with very high concentrations (> 1E20 cm-3) segregate at the NW sidewall surfaces, which confirms recent first-principles calculations and which results in modifications of the surface electronic properties that are sensitively probed by field-effect measurements. These findings are expected to be relevant also for doping studies of other non-catalytic III-V NW systems.