Nonradiative capture of hot photoelectrons by multiphonon emission in highly excited polar semiconductors

Room-temperature recombination dynamics of hot electron-hob plasma in highly excited polar semiconductors is analysed. A rate equation with Arrhenius dependence of carrier lifetime on the effective temperature is employed to consider the capture by deep centres via multiphonon emission (MPE) with the nonequilibrium LO phonons taken into account. The luminescence-intensity dependence on the pump intensity under quasi-stationary excitation conditions, as well as the shape of the luminescence-intensity transient kinetics, are shown to be strongly dependent on the height of the localization barrier. Typical manifestation of carrier temperature-activated capture by MPE is experimentally demonstrated both for quasi-steady-state and transient conditions in CdSe and CdS single crystals, respectively. Additionally, evidence, testifying that surface recombination in CdS nanocrystals embedded in a glass matrix exhibits features characteristic of nonradiative capture by MPE for carrier and phonon systems far from thermal equilibrium with the lattice, is presented. The relevant localization barriers are shown to lie within the 100-200 meV range.