Optical properties of indium-doped ZnO films

Indium-doped ZnO (IZO) films with low In content (<6at. %) were fabricated by rf helicon magnetron sputtering. The uniformity of the composites was confirmed by elemental analysis. The formation of an In-Zn-O solid solution was verified using X-ray diffraction (XRD) patterns. A wide, high-transmittance region (400-2000nm) and >80% transmittance in the window of fiber optics telecommunication (1.30-1.55 urn) were observed. The incorporation of indium enhances the optical transmission in the designated visible and infrared wavelengths. The optical band gap shows a slight blue-shift with increasing In doping which can be explained by the Burstein-Moss effect. The Urbach tail parameter E₀ increases with increasing indium content, which coincides with the increase in the full width half maximum (FWHM) of (0002) planes in XRD patterns. A decline in crystal quality with In incorporation in IZO films is also confirmed from photoluminescence (PL) spectra.