Electron Spin-Relaxation Times in p-type δ-doped GaAs/AlGaAs Double Heterostructures

Optically pumped GaAs is a promising material for probes of spin-polarized scanning tunneling microscopy. To increase the accuracy of the measurement, it is necessary to increase the spin polarization of excited electrons and their spin-relaxation time. A δ-doped GaAs/AlGaAs double heterostructure shows a larger spin-relaxation time than bulk GaAs. It has been reported that in this structure the effect of the exchange interaction between the electrons and excitons can easily be reduced by spatially separating the electrons and holes. However, the dependency of the relaxation time on the structural details has not been experimentally examined. In this study, we determine the optimum well width of the δ-doped double heterostructure which yields a long spin-relaxation time using time-resolved photoluminescence measurement. Spin-relaxation times of the e0→hh1 recombination and e0→lh1 recombination are individually characterized. The e0→hh1 recombination has the longer spin-relaxation time, and the longest relaxation time of τs20 ns is observed for the structure with a well 90 nm in width.