Spin injection into a single self-assembled quantum dot in a $p-i-n$ II-VI/III-V structure

The authors report on efficient spin injection from a $n-Zn0.96Mn0.04Se$ layer into an InAs single quantum dot (SQD) in a $p-i-n$ diode structure using magnetomicrophotoluminescence experiments. A circular polarization degree of up to 60% at $B=5T$ is obtained from the InAs single dot emission while no polarized light is observed in a structure with no electrical doping of any of its layers. A pronounced dependence of the spin injection efficiency on the external bias is found resulting in a strong decrease of the SQD circular polarization degree when the biasing is applied in the forward direction. The experiments emphasize the impact of excess energy and current flow on the spin injection efficiency in a SQD.