Dynamics of electron-hole pair recombination in semiconductor clusters

The kinetics of radiative electron-hole pair recombination in CdS and Cd{sub 3}As{sub 2} clusters (where the radius of the cluster is smaller than the de Broglie wavelength of photogenerated excitons) were studied with picosecond photon counting luminescence decay measurements over wide temperature and energy ranges. The decay profiles were quantitatively examined with several models. The decays are composed of two distinct time regimes, each with very different temperature and emission energy dependence. The first (fast) regime is attributed to an unusually efficient thermal repopulation mechanism. The second (slow) component is well described by a distributed kinetic model. The kinetic behavior of wide (CdS) and narrow (Cd{sub 3}As{sub 2}) band gap materials was remarkably similar when composed of clusters in the quantum confined regime.