Electrical and optical characterization of sputtered ZnO:Ga thin films doped with nitrogen

The electrical and optical characteristics of polycrystalline films zinc oxide:gallium, implanted consecutively with 40 keV and 80 keV nitrogen at doses of 1×10 ¹⁵ or 1×10 ¹⁶ cm ^-2 (ZnO:Ga:N ⁺ ), have been investigated. In photoluminescence spectra (PL) of studied samples taken at room temperature (RT), were identified three lines at 3.26 eV, 2.1 eV and 1.7 eV that were attributed to donor-to-acceptor defect level transitions. The intensity of these lines and the peaks' position depend on the parameters of the implantation and annealing processes. A Raman mode at around 505 cm ^-1 , appearing in the spectra of implanted and annealed layers, was assigned to N-related local vibrational modes. Evaluation of the electrical parameters' temperature dependence by means of Hall-effect measurements revealed a relatively flat region in the variations of concentration (n ~ 10 ²⁰ cm ^-3 ) and mobility changing 0.2-0.4 cm ² /Vs for the temperatures range 110-275 K. The logarithms of resistivity versus temperature is a straight line (ρ ~ 0.1-0.2 Ωcm).