Effects of interfacial suboxides and dangling bonds on tunneling current through nanometer-thick SiO2 layers

Abstract

Quantum-mechanical tunneling of charge carriers through nanometer-thick SiO2 layers is one of the key issues in Si-based electronics. Here, we report first-principles transport calculations of charge-carrier tunneling through nanometer-thick SiO2 layers in Si/SiO2/Si structures. We find that tunneling of holes in the valence bands occurs mainly via oxygen 2p orbitals perpendicular to Si-O-Si bonds, and it can be enhanced greatly by interfacial suboxides and dangling bonds in Si/SiO2 interfaces. Electrons in the conduction bands show tunneling behaviors sensitive to their wave vectors parallel to the interfaces, reflecting the six conduction-band minima in the bulk Si. Our results provide atomistic description of tunneling currents through SiO2 layers, and suggest that leakage current will be blocked more effectively if suboxides and dangling bonds are reduced.