Measurement of the spin detection efficiency of the s, p,d, and f shells in InAs QDs using optical pumping

We have carried out an optical pumping study of n-i-p AlGaAs(n)/GaAs(i)/AlGaAs(p) quantum wells (QW) structures that incorporate a single layer of InAs quantum dots (QDs) in the GaAs QW. The electron-hole pairs were photo-excited in the GaAs QWs and were subsequently captured by the InAs QDs. The resulting photoluminescence (PL) spectra contain features associated with recombination processes that involve electrons occupying the s- , p-, d-, and f-shells. The circular polarization of these features varies from 10 {\%} to 30 {\%} and increases monotonically from the s- to the f-shell. From these circular polarization measurements the spin detection efficiency for each shell was determined as function of temperature and longitudinal magnetic field applied along a direction perpendicular to the QD plane (z-axis). The optical pumping results, in combination with magneto-EL studies of Fe spin LEDs that have the same parameters and were grown under identical conditions were used to determine the injected electrons spin polarization in these devices.