EXCITONIC LIFETIMES IN (ZN,CD)SE ZNSE AND ZNSE/ZN(SE,S) QUANTUM WIRES/

The recombination dynamics of excitons in deep-etched (Zn,Cd)Se/ZnSe a nd ZnSe/Zn(Se,S) quantum wires has been investigated by time-resolved photoluminescence spectroscopy. At T = 2 K, the lifetime in ZnSe/Zn(Se ,S) wires is reduced for decreasing wire width from about 130 ps in th e two-dimensional reference to about 10 ps in the 60-nm-wide wires. Th e experimental data can be described with a surface recombination velo city of 5 x 10(5) cm/s at T = 2 K. In contrast, the low-temperature ex citon lifetime in (Zn,Cd)Se/ZnSe quantum wires does not vary significa ntly with wire width down to L(x) = 20 nm. This indicates at T = 2 K a strong suppression of carrier loss at the wire sidewalls most likely due to exciton localization effects. From high-temperature data, where localization effects can be neglected, we conclude that the surface r ecombination velocity in (Zn,Cd)Se/ZnSe quantum wires is about two ord ers of magnitude smaller than in the ZnSe/Zn(Se,S) system.