Phonon-assisted recombination in Fe-based spin LEDs

The electroluminescence (EL) spectra from Fe AlGaAs (n) GaAs AlGaAs (p) spin LEDs contain an e1 h1 excitonic feature; in addition, they exhibit new features not present in the photoluminescence (PL) spectra, that are "satellites" or "replicas" of the exciton. These satellites are red shifted with respect to e1 h1 by energies that are approximately equal to those of zone edge phonons in GaAs. The intensity of the replicas depends strongly on bias voltage. In the presence of a magnetic field the satellites become circularly polarized as σ+ but their polarization is always lower than that of e1 h1. The satellites are interpreted as due to recombination processes that involve zone edge electrons that tunnel into the GaAs quantum well. These processes occur simultaneously with the emission of zone-edge phonons. Our interpretation is supported by a numerical simulation of the properties of electrons tunneling through an Fe GaAs (n) Schottky barrier.