Tailoring the core electron density in modulation-doped Core-Multi-Shell nanowires

We show how a proper radial modulation of the composition of core-multi-shell nanowires critically enhances the control of the free-carrier density in the high-mobility core with respect to core-single-shell structures, thus overcoming the technological difficulty of fine tuning the remote doping density. We calculate the electron population of the different nanowire layers as a function of the doping density and of several geometrical parameters by means of a self-consistent Schr"odinger-Poisson approach: Free carriers tend to localize in the outer shell and screen the core from the electric field of the dopants.