Effect of the electric field on the carrier collection efficiency of InAs quantum dots

Individual and multi quantum dots of InAs are studied by means of microphotoluminescence in case when, in addition to the principal laser exciting photoluminescence, second infrared laser is used. It is demonstrated that the absorption of the infrared photons effectively creates free holes in the sample, which leads to both change in the charge state of a quantum dot and to the considerable reduction of their photoluminescence signal. The later effect is explained in terms of an effective screening of the internal electric field, facilitating the carrier transport along the plane of a wetting layer, by the surplus holes from the infrared laser. It is shown that the effect of quenching of quantum dot photoluminescence gradually disappears at increased sample temperature (T) and / or dot density. This fact is due to the essentially increased value of quantum dot collection efficiency which could be achieved at elevated sample temperatures for the individual quantum dots or even at low T for the case of multi quantum dots. It is suggested that the observed phenomena can be widely used in practice to effectively manipulate the collection efficiency and the charge state of quantum dot-based optical devices. E.S.M. gratefully acknowledges financial support from the Wenner{Gren Foundations and partial support from the program Low-Dimensional Quantum Structures of the Russian Academy of Sciences. V.D. is thankful to the Swedish Foundation for International Cooperation in Research and Higher Education (STINT) for financial support. 1