  Spin relaxation of electrons doped in InP quantum dots was studied by means
of luminescence pump-probe and Hanle measurements. Optical pumping makes spins
of doped electrons to be oriented in parallel to the helicity of the circularly
polarized excitation. The luminescence pump-probe showed the spin orientation
of the doped electrons decay on a millisecond time-scale. Hanle measurement
clarified the spin dephasing relaxation time of doped electrons is 1.7 ns which
is explained by the frozen fluctuation of nuclear spins.
