Wide-spectrum Mg and Ga co-doped ZnO–TCO thin films with introduced hydrogen grown by magnetron sputtering at room temperature

Transparent conductive hydrogenated Mg and Ga co-doped ZnO (HMGZO) thin films were deposited on glass substrates at room temperature by pulsed direct current magnetron sputtering, with hydrogen being introduced at various flow rates. X-ray diffraction results showed that these HMGZO thin films are polycrystalline, with a preferred (0 0 2) crystal-plane orientation. Hydrogen donors are responsible for the increase of carrier concentration and the lowest resistivity of 4.4 x 10(-3) Omega cm, with a carrier concentration of 1.92 x 10(2) cm(-3) and a mobility of 7.3 cm(2)/V s, was obtained at an H-2 flow rate of 9.0 sccm. The average transmittance of the HMGZO thin films exceeded 88.6% for wavelengths of 330-1100 nm. The optical band gap (E-g) increased from 3.41 to 3.74 eV with increasing the H-2 flow rate from 0 to 16.0 sccm. The widening of Eg could be attributed both to Burstein-Moss band-filling and to incorporation of Mg atoms. The electrical stability of HMGZO thin films with post thermal annealing process was also investigated. (C) 2014 Elsevier B.V. All rights reserved.