  We present nuclear spin relaxation measurements in GaAs epilayers using a new
pump-probe technique in all-electrical, lateral spin-valve devices. The
measured T1 times agree very well with NMR data available for T > 1 K. However,
the nuclear spin relaxation rate clearly deviates from the well-established
Korringa law expected in metallic samples and follows a sub-linear temperature
dependence 1/T1 ~ T^0.6 for 0.1 K < T < 10 K. Further, we investigate nuclear
spin inhomogeneities.
