  Time-resolved electrical spin transport is used to generate and probe spin
currents in GaAs electrically. We use high bandwidth current pulses to inject
phase-coherent spin packets from Fe into n-GaAs. By means of time-resolved
Faraday rotation we demonstrate that spins are injected with a clearly defined
phase by the observation of multiple Larmor precession cycles. We furthermore
show that spin precession of optically created spin packets in n-GaAs can be
probed electrically by spin-polarized photo-current pulses. The injection and
detection experiments are not direct reciprocals of each other. In particular,
we find that interfacial spin accumulation generated by the photocurrent pulse
plays a critical role in time-resolved electrical spin detection.
