TEMPERATURE-DEPENDENCE OF LOCALIZED AND FREE-EXCITON LIFETIME IN CDZNSSE ZNSSE SINGLE QUANTUM-WELLS/

Time-integrated and time-resolved photoluminescence of Cd0.3Zn0.7S0.06 Se0.94/ZnS0.06Se0.94 single quantum wells (QW) have been studied. The radiative recombination process is dominated by localized excitons whi ch have a constant lifetime of similar to 300 ps when the temperature is less than 130 K. As the temperature increases, localized excitons a re thermally activated to form free excitons which are stable up to ro om temperature because of the large exciton binding energy and strong confinement of electrons and holes in these QWs. Free exciton radiativ e recombination is thus dominated when temperature is in the 130 K to room temperature (295 K) range. The free exciton decay time of similar to 300 ps at 130 K increased linearly to similar to lns at 295 K. Thi s linear increase in exciton lifetime with temperature agrees with the theoretical prediction by considering the conservation of momentum re quirement for radiative recombination for excitons in QW. (C) 1998 Aca demic Press.