Temperature and doping dependence of spin-flip times in n-GaAs

Previously-reported time resolved photoluminescence experiments [1] in lightly-doped n-GaAs have been extended to provide additional measurements of T$_{1}$ spin-flip times as a function of temperature and of doping density. The samples studied were MBE-grown 1 micron thick layers of doping densities from 3E14 cm$^{-3}$ to 3E15 cm$^{-3}$. The technique was to use a pump pulse to inject spin polarized electrons and a probe pulse to read out the polarization at some later time; spin flips caused the polarization to decrease exponentially with pump-probe delay. Some measured T$_{1}$ spin-flip times (at low temperature, at low doping densities) were even longer than the previously-reported 1 microsecond value. Work supported by NSF, ACS/PRF, and Research Corporation. [1] J.S. Colton et al., Phys Rev B 69, 121307(R) (2004).