  With downscaling of electronic circuits, components based on semiconductor
quantum dots are assuming increasing relevance for future technologies. Their
response under external stimuli intrinsically depend on their quantum
properties. Here we investigate single-electron tunneling in hard-wall InAs/InP
nanowires in the presence of an off-resonant microwave drive. Our
heterostructured nanowires include InAs quantum dots (QDs) and exhibit
different tunnel-current regimes. In particular, for source-drain bias up to
few mV Coulomb diamonds spread with increasing contrast as a function of
microwave power and present multiple current polarity reversals. This behavior
can be modelled in terms of voltage fluctuations induced by the microwave field
and presents features that depend on the interplay of the discrete energy
levels that contribute to the tunneling process.
