Valence electron control and electron transport mechanisms oil the amorphous indium zinc oxide (IZO) films were investigated. The amorphous IZO films were deposited by dc magnetron sputtering using an oxide ceramic IZO target (89.3 Wt.% In2O3 and 10.7 wt.% ZnO). N-type impurity dopings, such as Sn, Al or F, could not lead to the increase in carrier density in the IZO. Whereas, H, introduction into the IZO deposition process was confirmed to be effective to increase carrier density. By 30% H-2 introduction into the deposition process, carrier density increased from 3.08 x 10(20) to 7.65 x 10(20) cm(-3), Which Must be originated in generations of oxygen vacancies or interstitial Zn2+ ions. Decrease in the transmittance in the near infrared region and increase in the optical band gap were observed with the 14, introduction, which corresponded to the increase in carrier density. The lowest resistivity of 3.39 x 10(-4) Omega cm was obtained by 10% H-2 introduction without substrate heating during the deposition. (c) 2005 Elsevier B.V. All rights reserved.