First-principles study of p-type ZnO by S–Na co-doping**Project supported by the Natural Science Foundation of Hubei Province, China (Nos. 2014CFB342, 2014CFB619) and the Doctoral Foundation for Scientific Research of Hubei University for Nationalities (No. MY2013B020).

Abstract

Using the first-principles method based on the density functional theory, the formation energy, electronic structures of S–Na co-doping in ZnO were calculated. The calculated results show that NaZn–SO have smaller formation energy than Nain–SO in energy ranges from –3.10 to 0 eV of , indicating that it opens up a new opportunity for growth the p-type ZnO. The band structure shows that the NaZn system is a p-type direct-band-gap semiconductor material and the calculated band gap (0.84 eV) is larger than pure ZnO (0.74 eV). The NaZn–SO system is also a p-type semiconductor material with a direct band gap (0.80 eV). The influence of S–Na co-doping in ZnO on p-type conductivity is also discussed. The effective masses of NaZn–SO are larger than effective masses of NaZn and the NaZn–SO have more hole carriers than NaZn, meaning the hole in the NaZn–SO system may have a better carrier transfer character. So we inferred that NaZn–SO should be a candidate of p-type conduction.