Defect Generation by Hydrogen at the Si- SiO₂ Interface

Hydrogen is known to passivate Si dangling bonds at the Si-SiO₂ interface, but the subsequent arrival of H⁺ at the interface causes depassivation of Si-H bonds. Here we report first-principles density functional calculations, showing that, contrary to conventional assumptions, depassivation is not a two-step process, namely, neutralization of H⁺ by a Si electron and subsequent formation of an H₂ molecule. Instead, we establish that H⁺ is the only stable charge state at the interface and that H⁺ reacts directly with Si-H, forming an H₂ molecule and a positively charged dangling bond ( P_b center). As a result, H-induced interface-trap formation does not depend on the availability of Si electrons.