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

Abstract

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 1.89×1015to2.11×1019cm−3 as the N2 flow rate decreases from 15to6SCCM (SCCM denotes cubic centimeter per minute at STP), i.e., increasing N2 flow rate above 6SCCM decreases the p-type carrier concentration. Microphotoluminescence (PL) spectra peaks are in the near-UV range and change from 384nm(3.23eV)to374nm(3.32eV) with increasing N2 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 (E2 high-frequency phonon mode for undoped ZnO film), 581 [A1 (LO) mode in ZnO:N film], 275, 508, 640, and 854cm−1 (local vibrational modes of Raman features in N-doped ZnO film).