Silicon-based molecular electronics

Molecular electronics on silicon has distinct advantages over its metallic counterpart. We describe a theoretical formalism for transport in semiconductor-molecule heterostructures, formally combining a semiempirical treatment of bulk silicon with a first-principles description of the molecular chemistry and its bonding with silicon. Using this method, we demonstrate that the presence of a semiconducting band-edge can lead to a novel molecular resonant tunneling diode (RTD) that shows negative differential resistance (NDR) when the molecular levels are driven by an STM potential into the semiconducting band gap. The NDR peaks show a clear polarity reversal, appearing for positive bias on a p-doped and negative for an n-doped substrate, a feature that is in agreement with recent experiments by Guisinger et al.(1,2.)