Transparent conductive Ga-doped MgxZn1−xO films with high optical transmittance prepared by radio frequency magnetron sputtering

Highlights: ► Transparent conductive Ga-doped MgxZn1−xO (GMZO) films were grown by sputtering. ► Structural, electrical, and optical properties of the films were clearly studied. ► Low thin film resistivity of 5.69 × 10−4 Ω cm was found with mobility of 28.5 cm2/V s. ► High optical transmittance over 96.6% was obtained in a visible wavelength range. -- Abstract: Transparent conductive Ga-doped MgxZn1−xO (GMZO) films were deposited on sapphire at room temperature using radio-frequency magnetron sputtering with different RF powers. The thickness of all films was controlled at 300 nm, and the lowest resistivity was obtained at an RF power of 50 W. This study investigates the influence of the post-annealing process on the structural, electrical, and optical properties of the films using X-ray diffraction (XRD), atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), Hall measurement, optical transmission spectroscopy, photoluminescence (PL) spectra, and X-ray photoelectron spectroscopy (XPS) spectra. The XRD (0 0 2) peak intensity and the spectral linewidth enhanced monotonically as the annealing temperature rose to 700 °C, indicating improved crystallinity in the GMZO thin films. A low thin film resistivity (ρ) of 5.69 × 10−4 Ω cm was obtained, along with electron mobility (μ) and carrier concentrations (n) of 28.5 cm2/V s and 3.85 × 1020 cm−3, respectively. XPS measurements were conducted to investigate the mechanism of the reduced thin-film resistivity after high-temperature annealing. The increased density of oxygen vacancies could contribute to the reduced resistivity after high-temperature annealing. Meanwhile, a high optical transmittance of over 96.6% was demonstrated in a wavelength range between 350 and 1100 nm