Stability and Optical Properties of the C-Doping-Induced Defects | Sergey Stolbov

Summary :
⁣Quantum information technologies have triggered enormous interest to the single-photon emitters (SPEs), such as local defects in wide-band-gap semiconductors. Recently, singlephoton emission was observed in carbon-doped hexagonal boron nitride (h-BN).1 To reveal the structure and formation energy of the defects, we select six possible C-based defects, including ones with simple substitutional doping and substitutional doping combined with extra vacancy formation. Our density-functional-theory-based calculations of optimized geometries and point phonon frequencies reveal that one of the selected defects (proposed elsewhere as SPE) is dynamically unstable and undergoes a structural transformation. We perform calculations of the electronic structure using the linear response approach (GW method) followed by calculations of the solution to the Bethe-Salpeter equation to obtain the excitation spectra of dynamically stable defects. Upon comparing the obtained results with the reported SPE spectra,1 I will show that only one of the considered defects has an excitation spectrum fitting the conditions for the observed single-photon emission. That is the defect formed upon substitution of an N-atom by carbon (CNdefect). Importantly, this defect is also found to be the most thermodynamically stable among those under consideration.