  We investigate the correlation between spin signals measured in
three-terminal (3T) geometry by the Hanle effect and the spin accumulation
generated in a semiconductor channel in a lateral (Ga,Mn)As/GaAs Esaki diode
device. We systematically compare measurements using a 3T configuration,
probing spin accumulation directly beneath the injecting contact, with results
from nonlocal measurements, where solely spin accumulation in the GaAs channel
is probed. We find that the spin signal detected in the 3T configuration is
dominated by a bias-dependent spin detection sensitivity, which in turn is
strongly correlated with charge-transport properties of the junction. This
results in a particularly strong enhancement of the detected spin signal in a
region of increased differential resistance. We find additionally that two-step
tunneling via localized states (LS) in the gap of (Ga,Mn)As does not compromise
spin injection into the semiconductor conduction band.
