Charged excitons in single CdTe quantum dots

Optical emission from individual n-type modulation-doped CdTe quantum dots (QDs) is presented. Exciton, biexciton and negatively charged exciton emission lines are identified in the micro-photoluminescence spectra. All these few-particle species are exposed to randomly fluctuating electric fields attributed to charges trapped in the vicinity of the QD. The resulting quantum-confined Stark effect, characteristic for each QD, is analyzed in detail. The correlation between the emission energies and the integrated intensities of the neutral and charged exciton permit one to confirm the identification of the charged species. The binding energies of the biexciton and charged exciton are found to sharply decrease with the magnitude of the local electric field.