Transparent conducting zinc oxide thin films doped with aluminum and molybdenum

Undoped ZnO, ZnO:Al (0.5, 1, and 2 wt % Al2O3), and ZnO:Mo (2 wt % Mo) films were deposited by radio-frequency magnetron sputtering. Optimal deposition temperature was found to be similar to 200 degrees C for all films. Electron mobilities of 48 cm(2) V-1 s(-1) were achieved for undoped ZnO films using a sputtering gas with H-2/Ar ratio of 0.3%; corresponding carrier concentrations were similar to 3 X 10(19) cm(-3). A target incorporating 0.5 wt % Al2O3 in ZnO yielded films with mobility of 36 cm(2) V-1 s(-1) and carrier concentration of 3.4 X 10(20) cm(-3). These films present comparable conductivity and lower free-carrier absorption than films grown from a target containing 2 wt % Al2O3. Mo was found to be an n-type dopant of ZnO, though electrical and optical properties were inferior to those of ZnO:Al. Temperature-dependent Hall measurements of ZnO:Al films show evidence of a different scattering mechanism than ZnO:Mo films. (c) 2007 American Vacuum Society.