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 enhancem ent of the ground-state PL are observed. This is explained by carrier trans fer 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 em issions with respect to the InAs band gap in the temperature range of 90-28 3 K is explained by stepwise carrier escape from the QDs via the excited st ates. (C) 2001 American Institute of Physics.