Studies of electron spin lifetimes in InGaAs:Al quantum wells

We have carried out optical pumping, Hanle and longitudinal Hanle studies of InGaAs:Al/GaAs single quantum wells. The circular polarization at zero magnetic field has a maximum around 50 K indicating that at low temperatures the recombination is associated with a bound electron. The measured spin lifetimes at low temperatures are an order of magnitude longer than those measured in reference GaAs/AlGaAs quantum wells. This is attributed to the suppression of the Dyakonov-Perel spin relaxation mechanism in this bound system. As the temperature is increased from 5 to 50 K the spin lifetimes decrease and become comparable to the lifetimes of the reference sample. In the longitudinal Hanle geometry the circular polarization increases with magnetic field and reaches a maximum at B $\approx $ 1.5 tesla. Beyond 1.5 tesla the circular polarization decreases. A series of polarization oscillations superimposed on the decreasing background with a periodicity of approximately 1 tesla is observed. These oscillations are tentatively attributed to the variations in the magnetic flux through the bound electron orbit. Work at SUNY was supported by ONR and NSF