Simulation of semiconductor-oxide interface atomic and electronic structure
The chemistry of the silicon-silicon dioxide interface is ideal from the point of view of low interface defect density. Any dangling electrons at the interface can be tied up by adding hydrogen so that the number of electron states in the band gap is small. Energy levels for the silicon-hydrogen bond lie well below the silicon valence band edge.
Atom-projected densities of states for the Si(001)-aSiO2 interface
The chemistry of the III-V oxide interfaces is poorly understood. Adding hydrogen is not a good solution for removing electronic states from the III-V band gap as arsenic-hydrogen bond energy levels, etc. lie around the III-V valence band edge.
In this project we aim to understand the electronic behaviour of silicon-silicon dioxide and silicon-hafnium dioxide interfaces using a combination of classical molecular dynamics and density functional theory. The figures below show structures generated for these interfaces using a combination of these techniques.
Electronic wave functions for dangling electron defects at the Si(001)-aSiO2 interface
The figure above shows that Si dimers form spontaneously at the interface but are not ordered as they are at clean Si(001) surfaces. This leads to a high defect density at the interface unless these are passivated by terminating dangling bonds by H atoms.
This work is sponsored by the Irish Higher Education Authority under the PRTLI-V grant.