The role of atomic hydrogen in Ge/Si core-shell nanowires

We investigate the role of atomic hydrogen in Ge/Si core-shell nanowires with first-principles calculations and present that the hole doping in the Ge/Si heterointerface is achievable through interstitial hydrogen mediated remote doping. This atomic hydrogen induced hole doping could generate one-dimensional hole gas in Ge/Si core-shell nanowires. Hydrogen prefers to be incorporated in the Si shell due to the lattice strain effect. As the charge transition energy level of the interstitial hydrogen in Si is lower than the valence band maximum of the Ge band, the electrons in the Ge core prefer to move toward the Si shell and become trapped by the interstitial hydrogen. This unique hydrogen energy level in the Ge/Si heterostructure between the Ge and Si valence band edges drives the electron transfer from the Ge core and induces holes states in the Ge core through remote hole doping. We also perform a quantum transport simulation and show that a high conductive hole channel in the Ge core can be generated when hydrogen is incorporated into the Si shell. Our investigation on the role of atomic hydrogen in the Ge/Si core-shell nanowire opens the possibility of manipulating the hole concentration by tuning the process conditions.