Electronic properties of InAs/GaAs quantum dots

摘要

We report a detailed study of the electronic properties of self-organized InAs/GaAs quantum dots (QDs) by photoluminescence (PL), time-resolved PL, and PL excitation (PLE) experiments. High-quality InAs/GaAs QDs of tunable size were obtained using the variable deposition amount approach in MBE-growth, yielding ultimately room-temperature emission at 1.3 μm for island area densities of ～400 /μm~(-2). The experiments emphasize the role of a slowed down carrier relaxation in the QDs, being important, for example, for energy transfer processes between QDs and the temperature dependence of the carrier capture processes. The quantum size effect of the excited-state spectrum is revealed in PLE experiments and shown to be in good agreement to numerical results for pyramidal QDs based on eight band k · p theory. Finally, phonon-assisted recombination processes are identified demonstrating an enhanced exciton-LO-phonon coupling. Excellent agreement with estimations in the adiabatic approximation suggests that this enhancement is the consequence of the particular quantum confinement and the piezoelectricity in the strained low-symmetry QDs.