spinleds

SpinLEDs are light-emitting diodes that employ spin-polarized carriers to influence the polarization of emitted light. In a spin-LED, electrons are injected into a semiconductor light-emitting region from a ferromagnetic contact or magnetized material, carrying a net spin polarization. Recombination of these spins with holes produces photons whose angular momentum is linked to the electron spin, yielding circularly polarized light. The measured degree of circular polarization of the emitted light serves as an indirect probe of the spin polarization of carriers inside the device. Spin relaxation and dephasing in the semiconductor limit the polarization and thus the efficiency of spin injection.

Common device concepts use GaAs- or GaN-based LEDs with ferromagnetic injectors such as ferromagnetic metals or diluted magnetic semiconductors; to mitigate conductivity mismatch at the metal–semiconductor interface, tunnel barriers or spin-polarized semiconductor contacts are employed. Structures are typically p-i-n or quantum-well active regions to enhance radiative recombination.

Experimentally, spin-LEDs have demonstrated electrical injection of spin and circularly polarized light, with significant progress in distinguishing room-temperature operation and improving polarization. However, achieving high spin injection efficiency at room temperature remains challenging due to spin relaxation, interface scattering, and material quality.

Applications include polarized light sources for photonic and quantum information systems, as well as exploratory components in spintronic integrated circuits. Research continues to improve injection efficiency, material systems, and device designs. See also spintronics.