Raman and Photoluminescence Study of Al,N-Codoped ZnO Films Deposited at Oxygen-Rich Conditions by Magnetron Sputtering

Optical properties of as-grown high nitrogen-doped ZnO:Al,N films (with a variation of nitrogen concentration from 2.3 to 4.3 atomic %) are studied by Raman, photoluminescence, and Fourier-transform infrared spectroscopy (FTIR). The intensity of mode A(1)(LO), peaked at 580 cm(-1), increases with increasing nitrogen concentration. The silent mode B-1(low) at 275 cm(-1) is clearly observed testifying increased disorder-activated scattering in ZnO. Photoluminescence spectra reveal near-band edge emission as well as several defect-related bands, the intensity of which increases with nitrogen content. The blue band (2.61 eV) can be related to the transition from shallow donor level to deep nitrogen acceptor level. Also, incorporation of nitrogen in ZnO lattice causes appearance of both Zn-i and O-i defects responsible for violet (3.08 eV) and yellow (2.16 eV) emission band, respectively. At the same time near-band edge emission of ZnO:Al,N films is not suppressed by simultaneously introduced Al and N impurities. Al compensates distortions in ZnO crystal lattice caused by nitrogen doping and, thus, stabilizes near-band edge emission.