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

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.