Ultraclean semiconductors are by definition unable to
superconduct because at low temperatures there are too few
carriers available to condense into the superconducting state.
In principle, one could introduce enough charge carriers into a
semiconductor, say by chemical doping. However, the necessary
doping is so high that it often damages the semiconductor
itself. Boron-doped diamond and silicon have been found to
superconduct at around and , respectively. In an article
published in the Physical Review Letters, Thomas Hermannsdörfer
and collaborators from the Dresden High Magnetic Field
Laboratory and the Forschungzentrum Dresden-Rossendorf in
Germany report superconductivity at about in gallium-doped
germanium at ambient pressure. Their first step is to use ion
implantation on germanium to introduce the necessary high
concentration of gallium dopants within a thin top layer.
However, heavy ion implantation severely damages the local
lattice structure of the germanium crystal. The challenge is to
therefore r