Nitrogen-doped p-type ZnO films prepared from nitrogen gas radio-frequency magnetron sputtering

Wide band gap nitrogen-doped p-type ZnO films are prepared by radio-frequency magnetron sputtering from a 99.99% purity ZnO target. The sputtering gas is Ar mixed with various flow rates of nitrogen gas. Hole concentrations increase from 1.89x10(15) to 2.11x10(19) cm(-3) as the N-2 flow rate decreases from 15 to 6 SCCM (SCCM denotes cubic centimeter per minute at STP), i.e., increasing N-2 flow rate above 6 SCCM decreases the p-type carrier concentration. Microphotoluminescence (PL) spectra peaks are in the near-UV range and change from 384 nm (3.23 eV) to 374 nm (3.32 eV) with increasing N-2 flow rate. The PL peaks agree with the band gap of bulk ZnO, which comes from the recombination of free excitons. Raman spectra show six peaks: 436 (E-2 high-frequency phonon mode for undoped ZnO film), 581 [A(1) (LO) mode in ZnO:N film], 275, 508, 640, and 854 cm(-1) (local vibrational modes of Raman features in N-doped ZnO film). (c) 2006 American Institute of Physics.