Ultrafast Photocarrier Relaxation Mechanisms in Sputter-Deposited CdTe Quantum Dot Thin Films

摘要

Photocarrier relaxation mechanisms in CdTe quantum dots in the strong confinement regime were investigated using femtosecond pump-probe measurements. The quantum dots were formed in films deposited on silica substrates using a sequential RF magnetron sputtering process with heat treatment to grow crystallites of various sizes. Size selection was achieved by tuning the laser to various wavelengths across the first excitation transition. The recombination mechanism showed a biexponential decay, which was fitted to a three-level model. It was shown that recombination occurs increasingly through the intermediate energy level as the size of the dots decreases. The nature of the intermediate level and the role of Auger recombination is discussed.