Characterization of gallium-nitrogen co-doped zinc oxide thin films prepared by RF diode sputtering

We investigated the possibility of achieving p-type zinc oxide (ZnO) by RF diode sputtering and gallium nitrogen co-doping. ZnO:Ga:N thin films were prepared with a different N-2 Content in Ar/N-2 working gas, ranging from 0 to 100%, and at a varying substrate temperature, from room temperature (RT) to 300 degrees C. A hole conduction with maximum carrier concentration of 2.6 x 10(18) cm(-3), mobility of 2 cm(2)/Vs and resistivity of 1.5 Omega cm resulted from deposition at RT with 100% N-2. It arose from N incorporation and formation of No acceptors. In the secondary ion mass spectrometry (SIMS) depth profiles of the co-doped films were observed NO/NO2 negative ions. Average transmittance (including Corning glass substrate) across the visible spectrum varied (60 divided by 66%) with increasing nitrogen content (50 divided by 100% N-2). As the substrate temperature increased (RT - 300 degrees C), highly transparent (T similar to 72-83%) and conductive (electron concentrations of 10(17)-10(19) cm(-3)) n-type ZnO:Ga:N films were attained. Reduction of optical band gap (E-g) (similar to 3.13-3.08 eV) was observed for co-doped ZnO films. Atomic force microscopy (AFM) images revealed that the films grown at RI have roughness of approximately 5.3 nm while roughness of those grown at 300 degrees C is approximately 3.9 nm. (C) 2011 Elsevier Ltd. All rights reserved.