Electronic structure calculations on gallium-vacancy defects in Si_1-xGe_x

Silicon germanium (Si_1 - xGe_x) has emerged as a mainstream nanoelectronic material and as such its defect processes and energetics are technologically important. In semiconductor alloys the interaction of intrinsic point defects such as vacancies with dopant atoms are critical for the physical properties of the material and impact nanoelectronic device performance. Gallium (Ga) is a p-type dopant in elemental and alloys group IV semiconductors and its interaction with vacancies can impact its diffusion and electronic properties. The gallium-vacancy (GaV) defect pairs are not thoroughly investigated in Si_1 - xGe_x random semiconductor alloys. Here we employ hybrid density functional theory (DFT) to study the electronic properties and binding energies in seven compositions of Si_1 - xGe_x. The prediction of the prevalent GaV pair in each composition is hindered by the large number of local environments that impact in turn the energetics of the defect pairs. To overcome this, we applied the special quasirandom structures (SQS) method and considered the lowest binding energy GaV pairs to the favourable one for every respective composition.