Carrier Multiplication in CdTe Quantum Dots by Single-photon Timing Spectroscopy

Carrier multiplication (CM) was observed in CdTe quantum dots (QDs) capped with tetradecylphosphonic acid (TDPA) at h nu/E-g > 2.5 by picosecond single-photon timing spectroscopy, where h nu and E-g are the excitation and the band gap energies, and the CM efficiency increased rapidly with the increase of h nu/E-g. No CM was observed less than the threshold value of h nu/E-g approximate to 2.5, which is close to that of CdSe QDs. As compared to a previous report by Nair and Bawendi, our result suggests that CM is sensitive to the QD surface conditions.