Band energy dependence of defect formation in the topological semimetal Cd3As2

Cadmium arsenide (Cd3As2) is a prototypical Dirac semimetal that manifests topological properties in a three-dimensional (3D) bulk material. In defect-free Cd3As2, the Fermi level EF lies at a minimum in the density of states at the Dirac point, but experimentally it forms with excess electron carriers and an elevated EF, thereby masking the topological features. To computationally study the self-doping of Cd3As2, we combine density functional theory (DFT) calculations for defect formation energies with quasiparticle self-consistent GW (QSGW) electronic structure calculations. We demonstrate an innate dependence of the point defect formation energies on carrier concentrations and use the QSGW calculated density of states to extrapolate formation energies to arbitrary electron concentrations. This approach allows the quantitative modeling of thermodynamic defect equilibria in topological semimetals and is used to predict how control of growth conditions might be utilized to achieve doping-neutral Cd3As2.