First-principles theory of tunneling currents in metal-oxide-semiconductor structures

Abstract

Ultrathin gate-oxide films and alternate dielectrics call for accurate modeling of tunneling currents. Available models, based on the effective-mass approximation, yield good fits to finite-bias data, but fail for infinitesimal biases. Here we report a first-principles theory of tunneling currents. We show that the conductance at infinitesimal bias is a ground-state property and can be calculated accurately using density-functional theory (DFT) and the local-density approximation (LDA) for exchange-correlation. At finite biases, however, a discontinuity in the exchange-correlation potential must be properly included. Challenges for both theory and experiments are identified.