Optical properties of p-type Al and N co-doped ZnO films

Effect of Al–N codoping ratio on the conducting and optical properties of ZnO films deposited by helicon wave plasma assisted radio frequency magnetron sputtering under various N2 gas flow is investigated. Hall measurements show that ptype ZnO thin films have been achieved with proper N2 flow rate. X-ray diffraction patterns indicate that all the films are highly c-axis oriented. Room temperature photoluminescence spectra show a strong near-band-edge emission. With increasing N doping, the intensity of the emission behaves an increased and then decreased trend while the full width at half maximum is narrowed and then widened. In addition, photoluminescence spectrum at 77 K in the p-type ZnO film with the highest hole concentration show a much stronger peak near 3.32 eV (due to N related neutral acceptor bound excitons), than at 3.36 eV (neutral donor bound excitons), and the acceptor energy level is estimated to be 186 meV.