P-doping concentration dependence of electron-spin dynamics in InGaAs quantum well-dot coupled structures applied with electric field

摘要

In the field of semiconductor spintronics, opto-spintronic devices that directly convert spin angular momentum of electrons into circularly polarized light have been studied. Ⅲ-Ⅴ semiconductor quantum dots (QDs) are expected as an optically active layer because of the suppressed carrier spin relaxation obtained via their strong quantum confinements. Since the loss of electron-spin information is unavoidable due to rapid spin relaxation in semiconductor barriers, it is necessary to control the spin polarization in QDs through an efficient injection of electron spins into them. We have previously studied the electric field control of spin polarity in ultrafast spin injection into p-doped QDs from a tunnel-coupled quantum well (QW) [1, 2]. We found that the spin polarity can be greatly controlled in the voltage range of ±0.5 V for the lightly p-doped QDs [2]. In this study, we have fabricated electric-field-effect optical devices using InGaAs QW-QD tunnel-coupled structures doped with 0, 5, and 15 holes per QD. Then, we have studied the electron-spin dynamics in QDs using circularly-polarized time-resolved photoluminescence (PL).