The nitrogen-vacancy defect in SiGe.

Defect processes and energetics in semiconducting alloys is scientifically and technologically important as silicon germanium (SiGe) is a mainstream nanoelectronic material. It is established that point defects and defect clusters have an increasing role in the physical properties of SiGe particularly with the ever-decreasing critical dimensions of nanoelectronic devices. Nitrogen-vacancy defects in SiGe are bound and have the potential to change the optical and electronic properties and thus need to be investigated as absolute control is required in nanoelectronic devices. The nitrogen-vacancy defects are not extensively studied in SiGe random semiconductor alloys. Here we employ density functional theory (DFT) in conjunction with the special quasirandom structures (SQS) method to calculate the binding energies of substitutional nitrogen-vacancy pairs (NV) in SiGe alloys. This is a non-trivial problem as the energetics of these defect pairs are dependent upon the nearest neighbour Ge concentration and the composition of SiGe. The criterion for NV stability is binding energy and here it is shown that the most bound NV defects will form in high Si-content SiGe alloys.