Degradation of quantum dots under nuclear irradiation and its influence on exciton spectra in semimagnetic semiconductors



The paper studies radiation-induced modification of energetic spectra of excitons in CdTe quantum dots (QDs) in a (Cd, Mn)Te matrix. Exciton levels in such system are very sensitive to the changes in Mn concentration due to the exchange interaction between magnetic Mn ions and charge carriers (the giant splitting effect). Radiation-enhanced diffusion causes Mn penetration into the QD that leads to the changes in the exciton level energy. We found the spatial distribution of Mn ions for different durations of the irradiation and performed quantum calculations of the energy of exciton states with the obtained Mn concentration profiles. The dependences of the position of the exciton levels and the splitting between the energy of exciton states with σ+ and σ polarizations on the irradiation parameters and the QD's radius have been investigated. The calculations show that the irradiation causes a large shift of exciton levels. The splitting between levels with σ+ and σ polarizations may be increased in the order of value due to the irradiation. The radiation effects are stronger for QD with smaller radius.