Critical conditions for the formation of p-type ZnO with Li doping.

The stability of Li dopants in ZnO is studied via first-principles calculations with electric dipole correction. The formation energies of substitutional Li (Li Zn ), interstitial Li (Li i ) and the Li Zn + Li i complex are calculated in large supercells and the results are extrapolated to the limit of an infinite-sized supercell. The stabilities of 2Li Zn and the Li Zn + Li i complex are found to depend on the temperature and absolute oxygen partial pressure. At normal experimental temperature (900 K), an extremely high absolute oxygen partial pressure (194 bar) is needed to break the coupling between Li Zn and Li i and thus form p-type ZnO. The reaction barrier and the absorbance spectra are also discussed.