Electronic energy levels and carrier dynamics in InAs/InGaAs dots-in-a-well structure investigated by optical spectroscopy

We investigate the electronic energy levels and carrier dynamics in InAs/InxGa1-xAs dots-in-a-well (DWELL) structure by comprehensive spectroscopic characterization over a temperature range from 10 to 300 K. The integrated photoluminescence (PL) intensity is observed to increase with raising temperature up to 100 K. Through combining the PL and PL excitation (PLE) analysis, we provide direct evidence that this anomalous temperature dependence of the PL spectrum is due to the carrier trapping in InGaAs quantum well at low temperature. A rate equation model is adopted to quantitatively describe the thermal escape and capture processes of carriers in the DWELL system. The origin of thermal activation energies for quantum dot PL quenching at higher temperatures is discussed referring to the electronic energy levels revealed by PLE spectra.