Theoretical Studies on the Stability and Positioning of Germanium-Vacancy (GeV) Color Centers in Diamond*

The germanium-vacancy (GeV) in diamond is structurally similar to the silicon-vacancy (SiV) in diamond and it is an optically active color center which has been investigated for applications in quantum information processing and quantum networks.^1,2 Recent work shows that when GeV^- centers are integrated into nanoscale diamond waveguides, the optical properties far surpass those seen using NV and SiV centers.³

In light of these exciting experiments, we have used density-functional theory to study the formation energy of the GeV center in diamond as a function of Fermi level and charge state. We have also calculated the diffusion barriers of GeV centers in diamond to guide experimental work on how best to position these color centers to improve the optoelectronic properties of doped novel nanoscale devices. Preliminary calculations show a diffusion barrier for the C vacancy that is significantly lower than that for the Si vacancy in SiC and that undoped diamond favors the formation of the GeV^- center in agreement with experiment.

[1] Y. N. Palyanov et al., Sci. Rep. 5, 14789 (2015).
[2] T. Iwasaki et al., Sci Rep. 5, 12882 (2015).
[3] M. K. Bhaskar et al., Phys. Rev. Lett. 118, 223603 (2017).