Electric-field control of optical-spin injection from an InGaAs quantum well to p-doped quantum dots

We demonstrate electric-field control of optical-spin injection from an In 0.1 Ga 0.9 As quantum well (QW) to p-doped In 0.5 Ga 0.5 As quantum dots (QDs), where spin-polarized electrons are optically generated in the QW and then injected into the QDs via tunneling. The injected spin polarization in the QDs is detected by circularly polarized photoluminescence. The results show that the spin polarization is a function of electric field applied across the layered QW-QD structure. Moreover, p-doping has a marked effect on the polarity and degree of the spin polarization, which can provide precise control of the spin injection to QDs by an electric field using this p-doped QD-QW system.