The spin Hall effect allows the direct detection of spins in semiconductors. In this study, electron spins in n-doped gallium arsenide are detected and the effects of n-type doping in gallium arsenide under drift are studied. It is found that the effects in the spin-polarized electron transport increase with increasing doping density in the moderate range, indicating that the introduction of n-type dopants increases the electron-spin lifetimes in gallium arsenide. However, the transport drifting by a high field shows no effects because of destroying the electron-spin polarization in n-doped gallium arsenide. The results are discussed in details.