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 and ZnSe/Zn(Se,S) quantum wires has been investigated by time-resolved photoluminescence spectroscopy. At $T=2\mathrm{}$ K, the lifetime in ZnSe/Zn(Se,S) wires is reduced for decreasing wire width from about 130 ps in the two-dimensional reference to about 10 ps in the 60-nm-wide wires. The experimental data can be described with a surface recombination velocity of 5×${10}^5$ cm/s at $T=2\mathrm{}$ K. In contrast, the low-temperature exciton lifetime in (Zn,Cd)Se/ZnSe quantum wires does not vary significantly with wire width down to $L_x=20\mathrm{}$ nm. This indicates at $T=2\mathrm{}$ 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 recombination velocity in (Zn,Cd)Se/ZnSe quantum wires is about two orders of magnitude smaller than in the ZnSe/Zn(Se,S) system.