Electro-Optical Properties of AZO Thin Films with Deposition & Heat treatment Conditions

AZO thin films are grown on a p-Si(111) substrate by RF magnetron sputtering. The characteristics of various thicknesses and heat treatment conditions are investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Hall effect and room-temperature photoluminescence (PL) measurements. The substrate temperature and the RF power during growth are kept constant at 400 degrees C and 200 W, respectively. AZO films are grown with a preferred orientation along the c-axis. As the thickness and the heat treatment temperature increases, the length of the c-axis decreases as Al3+ ions of relatively small ion radius are substituted for Zn2+ ions. At room temperature, the PL spectrum is separated into an NBE emission peak around 3.2 eV and a violet regions peak around 2.95 eV with increasing thickness, and the PL emission peak of 300 nm is red-shifted with increasing annealing temperature. In the XPS measurement, the peak intensity of Al(2)p and O-ll increases with increasing annealing temperature. The AZO thin film of 100 nm thickness shows values of 6.5 x 10(19) cm(-3) of carrier concentration, 8.4 cm(-2)/V.s of mobility and 1.2 x 10(-2) Omega.cm electrical resistivity. As the thickness of the thin film increases, the carrier concentration and the mobility increase, resulting in the decrease of resistivity. With the carrier concentration, mobility decreases when the heat treatment temperature increases more than 500 degrees C.