Temperature study of trap-related photoluminescence decay in CdSxSe1-x nanocrystals in glass

The trap-related photoluminescence dynamics in CdSxSe1-x nanocrystals (for x=0.24 and x=0.74) in glass were studied in the temperature interval 10-300 K. A close link between the temperature behavior of the photoluminescence decay rate and that of the photoluminescence efficiency was found, which indicates a dominant role of nonradiative recombination. The trap-related photoluminescence was interpreted as the recombination of a shallowly trapped electron with a hole in a deep trap. An exponential decrease (with a constant in the range 0.2-0.4 eV) in the density of the deep traps with increasing energy above the valence band was found. Apart from the Arrhenius type of temperature behavior of decay rate with the activation energy approximate to 50 meV, the Berthelot type (characteristic temperature approximate to 160 K) was also observed. The latter was modeled by carrier tunneling between localized sites and the energetic distribution of the tunneling distances was obtained. (C) 2000 American Institute of Physics. [S0021-8979(00)03407-1].