1. Ü. Özgür, Y.I. Alivov, C. Liu, A. Teke, M.A. Reshchikov, S. Doğan, V. Avrutin, S.J. Cho, H. Morkoç, A comprehensive review of ZnO materials and devices. JAP 98, 041301–042103 (2005)
2. O. Maksimov, Recent advances and novel approaches of p-type doping of zinc oxide. Rev. Adv. Mater. Sci. 24, 26–34 (2010)
3. P. Sharma, K. Sreenivas, K.V. Rao, Analysis of ultraviolet photoconductivity in ZnO films prepared by unbalanced magnetron sputtering. JAP 93, 3963–3970 (2003)
4. S. Dhara, P.K. Giri, Stable p-type conductivity and enhanced photoconductivity from nitrogen-doped annealed ZnO thin film. Thin Solid Films 520, 5000–5006 (2012)
5. Sh. Guo, J. Li, Z. Du, Investigation on intra-3d-shell transitions in Co-doped ZnO. Appl. Phys. A 121, 645–649 (2015)