Injection of spin polarized electrons from a metal into a semiconductor is demonstrated for a GaAs/(In,Ga)As light emitting diode covered with Fe. The circular polarization degree of the observed electroluminescence reveals a spin injection efficiency of 2%. The underlying injection mechanism is explained in terms of a tunneling process.
Electrical injection from the Heusler alloy Co 2 FeSi into ͑Al,Ga͒As is investigated for different growth temperatures T G of the injector layer. Depending on T G , the spin polarization of injected electrons in the semiconductor is determined by two competing mechanisms: actual spin injection at the Co 2 FeSi/ ͑Al, Ga͒As interface and ultrafast spin alignment in the ͑Al,Ga͒As layer. This layer is strongly affected by the thermally activated diffusion of Co, Fe, and Si during the growth of the Co 2 FeSi layers. Despite the electrical compensation and magnetic transformation in the underlying semiconductor structure, a spin-injection efficiency of at least 50% is achieved as deduced from the analysis of electroluminescence and time-resolved photoluminescence data.
P-type room-temperature conductivities as high as 50/Ω cm are achieved in cubic GaN layers by the concept of reactive codoping. We use Be as the acceptor species and O as the reactive donor to render isolated Coulomb scatterers into dipole scatterers. This concept allows us to achieve high hole mobilities and thus p-type conductivities.
We demonstrate room-temperature spin injection from the epitaxially grown ferromagnetic metal Fe3Si into the semiconductor GaAs. The injection efficiency is comparable to values previously obtained for the Fe∕GaAs and MnAs∕GaAs hybrid systems using the emission of similar (In,Ga)As∕GaAs light-emitting diodes for the detection of spin polarization. The temperature dependence of the detected polarization is explained by taking into account spin relaxation inside the semiconductor device.
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