Mitigate self-compensation with high crystal symmetry: A first-principles study of formation and activation of impurities in GaN

[Display omitted] •Activation of Si, Ge, C, Be, and Mg are studied for wurtzite and zincblende GaN.•Impacts of symmetricity on self-compensation are evidenced via vibrational analysis.•Fourfold higher hole concentration is achievable via zincblende GaN. Formation and activation energies of common impurities: silicon (Si), germanium (Ge), carbon (C), beryllium (Be), and magnesium (Mg) in wurtzite (wz-) and zincblende (zb-) GaN are investigated by first–principles calculations. Si and Ge are excellent donors with low activation energies (300 meV) and the latter has a strong self-compensation effect (the formation energy of Bei compensating donor is negative). Bei is energetically abundant in zb-GaN because it has a 0.66 eV lower formation energy than wz-GaN. This is attributed to the coherence of the symmetricity between the s-orbitals and the interstitial site. The acceptor activation energy of Mg in zb-GaN is found to be 153 meV, which is smaller than its value in wz-GaN, 226 meV. Vibrational analysis suggests that Mgi compensating donor is less favorable to form in zb- than wz-GaN, since the higher symmetricity of the interstitial site in zb-GaN renders a much smaller vibrational entropy. Contrarily, the differences are insignificant for the impurities residing on Ga sites due to the same tetrahedral symmetricity. The results evidence the importance of self-compensation effects, which can be mitigated by the higher crystal symmetry of zb-GaN.