  We report the application of time- and polarization-resolved
photoluminescence up-conversion spectroscopy to the study of spin capture and
energy relaxation in positively and negatively charged, as well as neutral,
InAs self-assembled quantum dots. When compared to the neutral dots, we find
that carrier capture and relaxation to the ground state is much faster in the
highly charged dots, suggesting that electron-hole scattering dominates this
process. The long spin lifetime, short capture time, and high radiative
efficiency of the positively charged dots, indicates that these structures are
superior to both quantum well and neutral quantum dot light-emitting diode
(LED) spin detectors for spintronics applications.

Materials Science