Optical investigations on the annealing behavior of gallium- and nitrogen-implanted ZnO

Gallium and nitrogen ions have been implanted into ZnO crystals and metal organic vapor phase epitaxy grown ZnO layers. Postimplantation annealing behavior in the temperature range between 200 and 900 degreesC has been studied by means of Raman scattering and low-temperature photoluminescence. The temperature for healing of the implantation-induced defects was found to be 800 degreesC. Implanted gallium acts as donor with a donor binding energy E-D of 53 meV, thus allowing the control of n-type doping in ZnO. From photoluminescence measurements of the donor-acceptor pair transition of a series of nitrogen-implanted ZnO samples we estimate the binding energy E-A of the nitrogen acceptor between 163 and 196 meV. Electrical characterization of nitrogen-implanted samples shows a behavior ranging from low n-type to highly compensated. But no unambiguous and reproducible type conversion could be achieved. (C) 2004 American Institute of Physics.