L. Besombes

Charged excitons in single CdTe quantum dots

Abstract 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.

Spin properties of trions in a dense quasi-2D electron gas

The reflection and photoluminescence spectra of modulation-doped CdTe/CdMgTe quantum-well structures have been studied. It was found that the magnitude and sign of the Zeeman splitting of the trion reflection line depend on the electron concentration in the quantum well, whereas the magnitude and sign of the splitting of the exciton line are absolutely the same for all the electron concentrations under study. In the photoluminescence spectra, the magnitude and sign of the Zeeman splittings for the exciton and trion were the same. This “renormalization” of the trion g factor is explained in terms of the model of combined exciton-electron processes.