Ab-initio study of donor-acceptor codoping for n-type CuO

Abstract

Single n-type dopant in CuO has either a deep donor level or limited solubility, inefficient in generating free electrons. We have performed ab-initio study of the donor-acceptor codoping to obtain n-type CuO. Our results show that N codoping can slightly improve the donor level of Zr and In by forming shallower n-type complexes (ZrCu-NO and 2InCu-NO), but their formation energies are too high to be realized in experiments. However, Li codoping with Al and Ga is found to be relatively easy to achieve. 2AlCu-LiCu and 2GaCu-LiCu have shallower donor levels than single Al and Ga by 0.14 eV and 0.08 eV, respectively, and their formation energies are reasonably low to act as efficient codopants. Moreover, Li codoping with both Al and Ga produce an empty impurity band just below the host conduction band minimum, which may reduce the donor ionization energy at high codoping concentrations.

Mechanistic insights of enhanced spin polaron conduction in CuO through atomic doping

“…The introduction of shallow states from Li doping is also in agreement with previous theoretical and experimental works. 28,29,50,51 To investigate the effects of Li doping on the transport of holes in CuO (i.e. the effect of Li on hole hopping mobility) we first focused on the electron−phonon contribution to the activation energy, E eÀph a .…”

“…To account for this issue, we applied the Hubbard U correction 60 with U = 7.5 eV, a well-established model for this material. 50,51,[61][62][63] All calculations were carried out in the open-source plane wave code Quantum ESPRESSO 64 with ultrasoft LDA pseudopotentials, 65 unless otherwise noted. The choice of LSDA+U instead of GGA+U was made because GGA+U was unable to give the correct monoclinic structure of CuO, while LSDA+U yielded a geometry of CuO within 5% of experimental values.…”