Charge state control in single InAs/GaAs quantum dots by external electric and magnetic fields

摘要

We report a photoluminescence (PL) spectroscopy study of charge state controlin single self-assembled InAs/GaAs quantum dots by applying electric and/ormagnetic fields at 4.2 K. Neutral and charged exciton complexes were observedunder applied bias voltages from -0.5 V to 0.5 V by controlling the carriertunneling. The highly negatively charged exciton emission becomes stronger withincreasing pumping power, arising from the fact that electrons have a smallereffective mass than holes and are more easily captured by the quantum dots. Theintegrated PL intensity of negatively charged excitons is affectedsignificantly by a magnetic field applied along the sample growth axis. Thisobservation is explained by a reduction in the electron drift velocity causedby an applied magnetic field, which increases the probability of non-resonantlyexcited electrons being trapped by localized potentials at the wetting layerinterface, and results in fewer electrons distributed in the quantum dots. Thehole drift velocity is also affected by the magnetic field, but it is muchweaker.