First came solid-state electronics, producing the field effect transistor
(FET), in which a tiny voltage applied to a gate enables a much larger
current to flow through a circuit. Next came optoelectronics, producing
the light emitting diode (LED), in which electrons and holes (the spaces
vacated by electrons) are made to combine and produce useful light (unfortunately
this does not include silicon, an infamous non-light-emitter, at least
until recently). Then came spintronics, producing circuit elements such
as magnetoresistive sensors, in which an electron polarization (the
direction of an electron's magnetic moment) is an important variable.
Now scientists would like to combine optical and magnetic features in
a single technology.
Some steps have already been taken: dilute magnet semiconductors (DMS),
materials doped with magnetic metal atoms, can be made ferromagnetic;
that is, they can be magnetized and will stay magnetic providing you
stay below the curie temperature (which is to magnets what the transition
temperature is to superconductors). Furthermore, polarized electrons
have been used to make polarized photons in the dilute magnet materials.
The latest advance is to make a silicon-compatible spintronics material
that functions at room temperature. Arthur Hebard (firstname.lastname@example.org,
352-392-8842) and his colleagues at the University of Florida show that
the semiconductor gallium phosphide (GaP) doped with manganese becomes
and stays magnetic above room temperature.
These results suggest that the related compounds, InGaP and AlInGaP,
which are already used in light emitting diode applications, might also
become magnetic when doped with Mn and thus be useful as polarized light
emitters. This should lead handily to spin-LEDs and spin-FETs (requiring
much small operating voltages than conventional FETs).
More promising still is possibility of integrating doped-Ga-P spin-FETs
and LEDs with silicon technology, the reigning industry standard material.
Finally, it should be noted that a result like this, involving the fine
tailoring of a material with dopant elements, necessitated a strong
collaboration between the physics department at Florida (Hebard) and
the department of materials science and engineering (Cammy Abernathy
and Steve Pearton) (Theodoropoulou
et al., Physical Review Letters, 2 Sept.)