Density functional theory simulations of amorphous high-κ oxides on a compound semiconductor alloy: A-Al 2O 3InGaAs(100)-(42), a-HfO 2InGaAs(100)-(42), and a-ZrO 2InGaAs(100)-(42)

Abstract

The structural properties of a-Al 2O 3In 0.5Ga 0.5As, a-HfO 2In 0.5Ga 0.5As, and a-ZrO 2In 0.5Ga 0.5As interfaces were investigated by density-functional theory (DFT) molecular dynamics (MD) simulations. Realistic amorphous a-Al 2O 3, a-HfO 2, and a-ZrO 2 samples were generated using a hybrid classical-DFT MD melt-and-quench approach and tested against the experimental properties. For each stack type, two systems with different initial oxide cuts at the interfaces were investigated. All stacks were free of midgap states, but some had band-edge states which decreased the bandgaps by 0-40. The band-edge states were mainly produced by deformation, intermixing, and bond-breaking, thereby creating improperly bonded semiconductor atoms. The interfaces were dominated by metal-As and O-InGa bonds which passivated the clean surface dangling bonds. The valence band-edge states were mainly localized at improperly bonded As atoms, while conduction band-edge states were mainly localized at improperly bonded In and Ga atoms. The DFT-MD simulations show that electronically passive interfaces can be formed between high- oxides dielectrics and InGaAs if the processing does not induce defects because on a short time scale the interface spontaneously forms electrically passive bonds as opposed to bonds with midgap states. © 2011 American Institute of Physics.