Electro-optical injection and detection
The principle underlying the spin-LED can be adapted to enable spin
detection — which is vital for real spintronic devices. In a spin-LED (top),
when a spin-polarized electron is injected from the ferromagnetic layer
(blue) into the semiconductor (orange and yellow) via a Schottky
barrier (purple), it recombines with a hole (red) and in doing so emits a
circularly polarized photon. The degree of circular polarization can be
used to estimate the magnitude of the injected spin polarization. This
process can also be reversed by shining circularly polarized light onto
the semiconductor structure, which generates a population of excited
spin-polarized electrons within the semiconductor (bottom).
Depending on the relative direction of the magnetization of the
ferromagnetic detector with respect to the photon polarization,
photo-excited electrons in the "up" (or "down", if the magnetization is
reversed) spin state can tunnel across the Schottky barrier into the
ferromagnetic layer, where they can be detected as an electrical signal.