Growth and doping control of Ge/Si and Si/Ge core-shell nanowires

Selective doping and band-offset in core-shell nanowire (NW) structures using germanium (Ge)/ silicon (Si) can realize a type of high electron mobility transistor (HEMT) structure in one-dimensional NWs by separating the carrier transport region from the impurity-doped region. Precise analysis, using Raman spectroscopy of the Ge optical phonon peak, can distinguish three effects: the phonon confinement effect, the stress effect due to the heterostructures, and the Fano effect. Using these techniques, we obtained conclusive evidence of hole gas accumulation in Ge/Si core-shell NWs. The control of hole gas concentration can be realized by changing the B doping concentration in the Si shell.