Abnormal temperature-dependent photoluminescence characteristics of stacked InAs self-assembled quantum dot structures grown by molecular beam epitaxy

We have investigated the temperature-dependent photoluminescence (PL) chara cteristics of stacked self-assembled InAs/GaAs quantum dot structures grown by molecular beam epitaxy (MBE). A step-like behavior of the peak energies of excitonic bands as a function of temperature is observed in two tempera ture ranges of 60-90 K and 120-150 K, while the envelope of the change of p eak energies basically follows the Varshini law with InAs parameters up to 150 K. The thermal activation energy of the electron-hole emission through a GaAs barrier in the quantum dots was measured to be 76 meV. We observed a n unusual increase of integrated photoluminescence intensity with temperatu re in the step regions, suggesting that the excitonic recombination in stac ked quantum dots occurs in a condition where higher oscillator strength occ urred with a certain lattice temperature. (C) 2001 Published by Elsevier Sc ience B.V.