Controlled generation of neutral, negatively-charged and positively-charged excitons in the same single quantum dot - art. no. 2119209

We report the controlled generation of neutral, negatively-charged and positively-charged excitons in the same single InAs quantum dot. The control parameters are a vertical electric field applied to a capacitor-like structure, in which the quantum dots are embedded, and optical pump power. The strong Coulomb blockade in quantum dots can be exploited to control the charge of excitons containing one hole, the neutral exciton, X-0, and singly negatively charged exciton, X1-. We show here how this concept can be extended to excitons containing two holes, the biexciton, 2X(0), and significantly the singly positively charged exciton, X1+. We support all these assignments with a Coulomb blockade model. For all dots, the emission from the X1- is redshifted relative to the neutral exciton, but surprisingly we observe blueshifts as well as small redshifts for X1+. (c) 2005 American Institute of Physics.