The nonlocal spin resistance is measured as a function of temperature in a
Fe/GaAs spin-injection device. For nonannealed samples that show minority-spin
injection, the spin resistance is observed up to room temperature and decays
exponentially with temperature at a rate of 0.018\,K−1. Post-growth
annealing at 440\,K increases the spin signal at low temperatures, but the
decay rate also increases to 0.030\,K−1. From measurements of the
diffusion constant and the spin lifetime in the GaAs channel, we conclude that
sample annealing modifies the temperature dependence of the spin transfer
efficiency at injection and detection contacts. Surprisingly, the spin transfer
efficiency increases in samples that exhibit minority-spin injection.Comment: 10 pages, 4 figure
