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Spin and population dynamics of photoexcited carriers in GaAs/AlGaAs and InGaAs/InP quantum wells is investigated from 5K to 300K, revealing transition between excitonic and free carrier spin-relaxation at intermediate temperatures. Localisation is found to prolong spin relaxation of excitons by two orders of magnitude.

Spin and population dynamics of photoexcited carriers in GaAs/AlGaAs and InGaAs/InP quantum wells is investigated from 5K to 300K, revealing transition between excitonic and free carrier spin-relaxation at intermediate temperatures. Localisation is found to prolong spin relaxation of excitons by two orders of magnitude.

Spin dynamics of photoexcited carriers in GaAs/AlxGa1-xAs quantum wells have been investigated in a wafer containing twelve different single quantum wells, allowing full investigation of well-width and temperature dependences with minimal accidental variations due to growth conditions. The behavior at low temperatures is dominated by excitonic effects, confirming results described in detail by others. Between 50 and 90 K there is a transition from excitonic to free-carrier-dominated behavior; both the temperature and time scale of the transition are in excellent agreement with a theoretical model for exciton dissociation. Above 90 K we find two-component spin decays consisting of an unresolved component (faster than 2 ps) associated with exciton dissociation and hole spin-relaxation and a longer-lived component that yields the electron...