Millisecond spin-flip times of donor-bound electrons in GaAs
  We observe millisecond spin-flip relaxation times of donor-bound electrons in high-purity n-GaAs . This is three orders of magnitude larger than previously reported lifetimes in n-GaAs . Spin-flip times are measured as a function of magnetic field and exhibit a strong power-law dependence for fields greater than 4 T . This result is in qualitative agreement with previously reported theory and measurements of electrons in quantum dots. 
Kai-Mei C. Fu, Wenzheng Yeo, Susan Clark, Charles Santori, Colin   Stanley, M. C. Holland, and Yoshihisa Yamamoto