Influence of quantum dot density on excitonic transport and recombination in CdZnTe/ZnTe QD structures

We report on dynamics of excitons in CdxZn1-Te-x/ZnTe quantum dots (QDs) and present information of excitonic transport and recombination. Due to different growth methods, samples with different QD's densities were obtained. Time-resolved measurements reveal three decay mechanisms: (i) radiative recombination of excitons in the individual QDs; (ii) thermally activated escape of excitons and (iii) escape due to tunneling (hopping). In the high QD-density samples the hopping (r(HB) = 2700 ns(-1)) is two orders of magnitude more efficient than in the low QD-density samples (r(HB)=33 ns(-1)). Radiative recombination rates are similar in both types of samples, r(R) = 1-1.3 ns(-1). Due to the good radiative to nonradiative recombination ratio, the low-density QDs can be a potential source of entangled photon pairs. (C) 2004 Elsevier Ltd. All rights reserved.