Abnormal temperature behavior of photoluminescence from self-assembled InAs/AlAs quantum dots

We report on the temperature dependence of photoluminescence (PL) from self-assembled InAs/AlAs quantum dots (QDs). In the temperature range of 6–90 K, an abnormal blueshift of the first excited-state emission and an enhancement of the ground-state PL are observed. This is explained by carrier transfer within spatially coupled QDs with a reduced barrier between, which give rise to a small activation energy of about 2 meV. Based on the analysis of the PL intensities, the rapid redshift of the ground- and excited-state emissions with respect to the InAs band gap in the temperature range of 90–283 K is explained by stepwise carrier escape from the QDs via the excited states.