Microwave Assisted Tunneling in Hard-Wall InAs/InP Nanowire Quantum Dots

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 modeled in terms of multi-photon processes and presents features that depend on the type of QD orbitals involved in the tunneling process and on the relevant virtual states in the leads.