Note, that a direct analytical approach is not applicable in this case as most of the dopant is solidified on the surface of crystals and not actually included in the lattice. The concentrations were consistently found to be ~0.3 at% when doping with As and Sb. Particularly valuable data was obtained in experiments where EDX spectra were recorded from a thin section from the middle part of a crystal. The concentrations were found to be ~0.2 at%, which is only very slightly lower than those from local parts of the surface. This value could be considered the thermodynamic solubility of As and Sb in ZnO at the synthetic conditions.