UK researchers are close to demonstrating controlled
manipulation of electron spins in gated devices using the InAs and
InSb family of narrow bandgap materials.
The lifetime of electrons with defined spins injected into these
materials is significantly shorter than in wide gap semiconductors
such as GaAs, but they offer other advantages.
"InAs is unique in that when a metal is put down on top of it,
the contact is Ohmic and not a Schottky barrier," explained Dr
Lesley Cohen, reader in solid state physics at Imperial College.
"So it's a perfect template for creating designer barriers. You
don't have to live with the natural barrier that all other
semiconductors present."
The materials also have higher room temperature mobility, and
the potential to control a spin with a gate once it is injected is
much greater. Cohen said the reduced lifetime is far from a
showstopper.
"It's in gating these structures where the real spin transistor
applications are. A gate can go down comfortably to within a
micron, so as long as you can drift it [a spin] in a micron in
10-100ps you should be all right."
Imperial is one of a handful of university groups pursuing
InAs/InSb devices. "We are very close to demonstration," said
Cohen.