Electrical spin injection into InGaAs quantum dots

We report on the injection of electron spins into InGaAs quantum dots with an efficiency of up to 60%. This injection is observed in p-i-n light-emitting diode structures using the diluted magnetic semiconductor ZnMnSe as spin aligner (spin-LED). The degree of spin polarization is deduced from the circular polarization degree of the photons emitted when the injected electrons recombine in the quantum dots with unpolarized holes. We observe a strong energy dependence of the polarization degree with a strong increase starting from zero to a high value on the high energy side of the emission spectrum. To study the origin of this dependence, we compare results of two quantum-dot samples with emission peaks at 1.2 eV and 1.33 eV, respectively. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)