Doping with P-based and Zn + X dopants often leads to formation of smaller (10-20 µm) crystallites with no apparent shape and abundant inclusions on the surface (Fig. ). Optically such samples look like particles with rough surface, and sometimes the color might differ within one particle suggesting polycrystalline nature of the latter. Given that there were no reproducibly obtained phosphorus-doped single crystals, P-doped samples were partly excluded from further studying.