Room-temperature spin-conserved electron transport to semiconductor quantum dots using a superlattice barrier

To realize the optical transfer of electron spin information, developing a semiconductor layer for efficient transport of spin-polarized electrons to the active layers is necessary. In this study, electron spin transport from a GaAs/Al_0.3Ga_0.7As superlattice (SL) barrier to In_0.5Ga_0.5As quantum dots (QDs) is investigated at room temperature through a combination of time-resolved photoluminescence and rate equation analysis, separating the two transport processes from the GaAs layer around the QDs and SL barrier. The electron transport time in the SL increases for a thicker quantum well (QW) of SL due to the weaker wavefunction overlap between adjacent QWs. Additionally, the degree of conservation of spin polarization during transport varies with QW thickness. Rate equation analysis demonstrates an electron transport from SL to QDs while maintaining a high spin polarization for thick QWs. The achieved spin-conserved electron transport can be attributed to the combination of electron transport being sufficiently faster than the spin relaxation in SL and the suppressed spin relaxation in the p-doped GaAs layer capping the QDs. The findings indicate that SL is a promising candidate as an electron spin transport layer for optical spin devices.