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 NW grown by catalyst-free molecular beam epitaxy using 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-10 cm range. This behavior coincides with the incorporated Si dopant concentrations in the bulk part of the NW, suggesting the absence of compensation effects. Importantly, excess Si dopants with very high concentrations (>10 cm) segregate at the NW sidewall surfaces, which confirms recent first-principles calculations and 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 noncatalytic III-V NW systems.