Crystalline Size Effects on Texture Coefficient, Electrical and Optical Properties of Sputter-deposited Ga-doped ZnO Thin Films

C-axis oriented Ga-doped ZnO (GZO) films with various thicknesses were deposited on glass substrate by radio frequency (RF) magnetron sputtering. The dependence of crystal structure, electrical, and optical properties of the GZO films on crystalline size were systematically studied. The results showed that the texture coefficient of (002) peak (TC₍₀₀₂₎) decreases with increasing crystalline size. The Hall mobility μ was reciprocal to electron effective mass and the fitted relaxation time τ was 0.11±0.01μs. With the increase of average crystalline size, the resistivity increased slightly, which is caused by the competition of (002) and (101) plane, introducing in some defects and leading to carrier density reduction. The optical band gap was in the range from 3.454 to 3.319eV with increasing crystalline size from 26.96 to 30.88nm, showing a negative relationship. The dependence of optical band gap (Egop) on the crystalline size (R) can be qualitatively explained by a quantum confinement effect. The relationship between Egop and R of GZO films suggests that tuning up optical properties for desired applications can be achieved by controlling the crystalline size.