Nano-engineered structures are disclosed, incorporating nanowhiskers of high mobility
conductivity and incorporating pn junctions. In one embodiment, a nanowhisker of a first semiconducting material has a first
band gap, and an
enclosure comprising at least one second material with a second
band gap encloses said nanoelement along at least part of its length, the second material being doped to provide opposite
conductivity type charge carriers in respective first and second regions along the length of the of the nanowhisker, whereby to create in the nanowhisker by transfer of charge carriers into the nanowhisker, corresponding first and second regions of opposite
conductivity type charge carriers with a region depleted of free carriers therebetween. The
doping of the
enclosure material may be degenerate so as to create within the nanowhisker adjacent segments having very heavy
modulation doping of opposite conductivity type analogous to the heavily doped regions of an Esaki
diode. In another embodiment, a nanowhisker is surrounded by
polymer material containing
dopant material. A step of
rapid thermal annealing causes the
dopant material to diffuse into the nanowhisker. In a further embodiment, a nanowhisker has a
heterojunction between two different intrinsic materials, and
Fermi level pinning creates a pn junction at the interface without
doping.