Convex-shaped decay curve of carriers in a vertically coupled InAs/GaAs quantum dot.

In a study using time-resolved photoluminescence (PL) to examine the carrier dynamics of a vertically coupled InAs/GaAs quantum dot (QD) of 20 periods, we observed an initial slow carrier decay followed by a fast decay. The time at which the transition from slow to fast decay occurred increased on going to lower QD states at a fixed excitation power, and increased with increasing excitation intensity at a fixed QD state. This behavior is attributed to the relatively efficient vertical transfer of carriers in the vertically coupled InAs/GaAs QD. In addition, this vertical carrier transfer makes the rise of the PL signal slower at lower-energy states. This peculiar carrier dynamics behavior was not observed in a single-layered QD or in a vertically uncoupled QD of 20 periods. [ABSTRACT FROM AUTHOR]