Individual InAs/GaAs quantum dots are studied by micro-photoluminescence. By varying the strength of an applied external magnetic field and/or the temperature, it is demonstrated that the charge state of a single quantum dot can be tuned. This tuning effect is shown to be related to the in-plane electron and hole transport, prior to capture into the quantum dot, since the photo-excited carriers are primarily generated in the barrier.

We report on magneto-photoluminescence studies of InAs/GaAs quantum dots (QDs) of considerably different densities, from dense ensembles down to individual dots. It is found that a magnetic field applied in Faraday geometry decreases the photoluminescence (PL) intensity of OD ensembles, which is not accompanied by the corresponding increase of PL signal of the wetting layer on which ON are grown. The model suggested to explain these data assumes considerably different strengths of suppression of electron and hole fluxes by a magnetic field. This idea has been successfully checked in experiments on individual ON, where the PL spectra allow to directly monitor the charge state of a OD and, hence, to conclude about relative magnitudes of electron and hole fluxes toward the QD. Comparative studies of different individual QDs have revealed that the internal electric field in the sample (which was altered in the experiments in a controllable way) together with an external magnetic field will determine the charge state and emission intensity of the QDs.

Micro-photoluminescence in the presence of an external magnetic field is employed to study individual InAs/GaAs quantum dots (QDs). By varying the strength of the applied magnetic field, the charge state of the QD is tuned from a double negatively charged exciton to a neutral exciton. This effect is shown to be related to carrier transport in the QD-plane prior to capture into the QD. The temperature dependence of the tuning effect is discussed. © 2009 IEEE NANO Organizers.

Individual InAs/GaAs quantum dots (QDs) are studied with micro-photoluminescence in the presence of an applied external magnetic field. Attention is focused on the redistribution between the spectral lines of a single QD observed at increased external magnetic field when the magnetic field is applied parallel to the growth direction (Faraday geometry). The effect is shown to be transport related as the electron drift velocity in the QD-plane is decreased by the applied magnetic field and this affects the probability for electron capture into the QD.

A microphotoluminescence study of single InAs/GaAs quantum dots (QDs) in the presence of an applied external magnetic field is presented. Attention is focused on the redistribution between the spectral lines of a single QD observed at increasing magnetic field parallel to the growth direction (Faraday geometry). The redistribution effect is explained by considering the electron drift velocity in the QD plane that affects the probability for capture into the QD. In contrast, no redistribution is observed when applying the magnetic field perpendicular to the growth direction (Voigt geometry).

A low-temperature micro-photoluminescence (μ-PL) investigation of InAs/GaAs quantum dots (QDs) exposed to a lateral external electric field is reported. It is demonstrated that the QDs PL signal could be increased several times by altering the external and/or the internal electric field. The internal field in the vicinity of the dots could be altered by means of an additional infra-red laser. We propose a model, which is based on an essentially faster lateral transport of the charge carriers achieved in an external electric field. Consequently, also the capture probability into the dots and subsequently the dot luminescence is also enhanced. The results obtained suggest that the lateral electric fields play a major role for the dot luminescence intensity measured in our experiment.