Comparative study of quaternary Mg and Group III element co-doped ZnO thin films with transparent conductive characteristics

Mg and Ga co-doped ZnO (Mg_xGa_yZn_zO, x + y + z = 1, x = 0.05, y = 0.02 and z = 0.93, MGZO), Mg and Al co-doped ZnO (Mg_xAl_yZn_zO, x + y + z = 1, x = 0.05, y = 0.02 and z = 0.93, MAZO), Mg and In co-doped ZnO (Mg_xIn_yZn_zO, x + y + z = 1, x = 0.05, y = 0.02 and z = 0.93, MIZO), Mg doped ZnO (Mg_xZn_yO, x + y = 1, x = 0.05 and y = 0.95, MZO) and pure ZnO thin films have been prepared on the glass substrates by RF magnetron sputtering. Their structural, morphological, compositional, electrical, and optical properties were characterized. The X-ray diffraction patterns showed that all the thin films were grown as a hexagonal wurtzite phase with c-axis preferred orientation without secondary phase. The (0002) peak positions of MGZO, MAZO and MIZO thin films were not significantly changed. The cross-section field emission scanning electron microscopy images of MGZO, MAZO and MIZO thin films showed that all the thin films have a columnar structure with dense morphology. The MGZO thin film showed the best electrical characteristics in terms of the carrier concentration (3.7 × 10²⁰/cm³), charge carrier mobility (8.39 cm²/Vs), and a lower resistivity (1.85 × 10^{- 3}cm). UV-visible spectroscopy studies showed that the MGZO, MAZO and MIZO thin films exhibit high transmittance over 85% in the visible region. The MGZO thin films showed wider optical band gap energy of 3.75 eV.