Comparative magneto-photoluminescence study of ensembles and of individual InAs quantum dots.

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 QD ensembles, which is not accompanied by the corresponding increase of PL signal of the wetting layer on which QDs are grown. The model suggested to explain these data assumes considerably different strengths of suppression of electron and hole fluxes by a magnetic field.

Enhancement of the luminescence intensity of InAs/GaAs quantum dots induced by an external electric field.

InAs/GaAs quantum dots have been subjected to a lateral external electric field in low-temperature microphotoluminescence measurements. It is demonstrated that the dot PL signal could be increased several times depending on the magnitude of the external field and the strength of the internal (built-in) electric field, which could be altered by an additional infrared illumination of the sample. The observed effects are explained by a model that accounts for the essentially faster lateral transport of the photoexcited carriers achieved in an electric field.

Effects of separate carrier generation on the emission properties of InAs/GaAs quantum dots.

Individual quantum dots have been studied by means of microphotoluminescence with dual-laser excitation. The additional infrared laser influences the dot charge configuration and increases the dot luminescence intensity. This is explained in terms of separate generation of excess electrons and holes into the dot from the two lasers.