Inelastic cotunneling in the Coulomb-blockade transport of donor-atom transistors

Abstract

We report finite-bias characteristics of electrical transport through phosphorus donors in silicon nanoscale transistors, in which we observe inelastic-cotunneling current in the Coulomb-blockade region. The cotunneling current appears like a resonant-tunneling current peak emerging from the excited state and sustain within the blockade regions. These cotunneling features are unique, since the inelastic-cotunneling currents have so far been reported either as a broader hump or as a continuous increment of current. This finding is ascribed purely due to excitation-related inelastic cotunneling involving the ground and excited states. Theoretical calculations were performed for a two-level quantum dot, supporting our experimental observation.