Annealing Behavior of Defects in Multiple-energy Nitrogen Implanted ZnO Bulk Single Crystal

Multiple-energy nitrogen ions (energies: 1 to 100 keV and a net concentration: 2.24 x 10(20) cm(-3)) are implanted into ZnO bulk single crystals grown by the hydrothermal method. Rutherford backscattering-channeling studies show the presence of displaced Zn atoms (Zn-i) of about 4 % in as-implanted samples. An A-emission band related to the interstitial oxygen (O-i) is observed at 580 nm in 600 degrees C-annealed samples, and a new emission appears at 515 nm in 800 degrees C-annealed samples. It is proposed that the new emission band consists of the superposition of the green band (similar to 525 nm) observed in unimplanted ZnO and the residual A-emission band. In 800 degrees C-annealed samples, a band to acceptor transition at 3.26 eV is also observed in addition to a donor to acceptor pair transition, suggesting that nitrogen acceptor is located at about 180 meV above the valence band. A thermally stimulated current peak, P-1 (165 meV), which has been attributed to a native point defect, observed in unimplanted samples almost disappears in nitrogen-implanted samples annealed at 800 degrees C.