Energy level structure and electron relaxation times in InAs∕InxGa1−xAs quantum dot-in-a-well structures

Complementary interband and intraband optical spectroscopic techniques are used to investigate the band structure and carrier relaxation times in technologically important InAs∕InGaAs∕GaAs quantum dot-in-a-well (DWELL) structures. We determine the dot ground to first excited state energies to be 42meV in the conduction band and 18meV in the valence band. Using intraband pump-probe experiments, electron relaxation times from the well states to the dot ground state are measured to be ∼5ps at 10K. Our results provide important parameters for the design and simulation of DWELL-based interband lasers and intraband midinfrared photodetectors.