RADIATIVE LIFETIMES OF EXCITONS IN QUANTUM WIRES

The excitonic population lifetime and its temperature dependence is me asured in nanometer-scale quantum wires. The measurements were perform ed on two cleaved-edge overgrown GaAs quantum-wire systems, in which t he lateral dimensions are comparable to the dimensions of a reference quantum well and an easy comparison between them is straightforward. T he excitonic population decay time in the wires is less sensitive to t emperature changes than that in the wells. Whereas the latter is linea r with temperature, the former is roughly proportional to the square r oot of the temperature. Consequently, the decay times of the photolumi nescence from the wires are longer than those from the wells at low te mperature, but shorter at higher temperatures. From the temperature de pendence of the lifetimes, which is an unambiguous signature of a one- dimensional system, we find the intrinsic radiative lifetime of excito ns in quantum wires. They are an order of magnitude longer than in qua ntum wells.