Identification of Acceptor States in Li-N Dual-Doped p-Type ZnO Thin Films

Li-N dual-doped p-type ZnO (ZnO:(Li,N)) thin films are prepared by pulsed laser deposition. The optical properties are studied using temperature-dependent photoluminescence. The Li_Zn-N_O complex acceptor with an energy level of 138meV is identified from the free-to-neutral-acceptor (e, A⁰) emission. The Haynes factor is about 0.087 for the Li_Zn-N_O complex acceptor, with the acceptor bound-exciton binding energy of 12meV. Another deeper acceptor state located at 248meV, also identified from the (e, A⁰) emission, is attributed to zinc vacancy acceptor. The two acceptor states might both contribute to the observed p-type conductivity in ZnO:(Li,N).