Carrier and spin dynamics in charged quantum dots

Carrier and spin dynamics are measured in neutral, positively and negatively charged quantum dots using polarization-sensitive time-resolved photoluminescence. Carrier capture rates are observed to be strongly enhanced in charged quantum dots, suggesting that electron-hole scattering dominates this process. For positive quantum dots, the enhanced spin-polarized electron capture rate eliminates loss of electron spin information in the GaAs barriers prior to capture, resulting in strong circularly-polarized emission. Comparison of spin relaxation times in positively charged and neutral quantum dots reveals a negligible influence of the large built-in hole population, in contrast to measurements in higher-dimensional p-type semiconductors. The long spin lifetime, short capture time, and high radiative efficiency of the positively charged quantum dots indicates that these structures axe superior to both quantum wells and neutral quantum dots for spin detection using a spin light-emitting diode.