2018 年 61 巻 5 号 p. 315-324
Growth and structural properties of self-assembled quantum dots (QDs) of III-V compound semiconductors such as InGaAs by molecular beam epitaxy are described. The dynamics of photo-excited carriers are detected by time-resolved photoluminescence. Time-dependent injection processes of carriers and spin-polarized ones from barriers into QDs are studied, which are largely affected by a state-filling effect characteristic in the QD. This filling effect can be suppressed at high temperatures or in high-density QD ensembles. Vertically coupled QDs with a 2-dimensional electron system of quantum well (QW) are proposed for the purpose of efficient capture and injection of spin-polarized electrons from layered structures into QDs. Ultrafast spin-conserved tunneling with time constants ranging from 5 to 20 ps, depending on the barrier thickness from 2 to 8 nm, from the QW into the QDs is demonstrated with sufficiently high rates of spin conservation more than 90%.
