Modulation of carrier density in indium-gallium-zinc-oxide thin film prepared by high-power impulse magnetron sputtering

Amorphous indium-gallium-zinc-oxide (alpha-IGZO) thin films were prepared by high-power impulse magnetron sputtering. The film composition and properties were investigated. The films were zinc-rich when compared to the target material due to the highest sputtering yield, least collision scattering and lowest self-sputtering yield of zinc species among the metallic sputtered species. The carrier-density in the thin film was modulated by the process pressure. Increasing process pressure raised more oxygen radicals and enhanced the oxygen binding ability of the Ga additives. Therefore, the oxygen vacancies were passivated thereby the carrier density was inhibited. Specifically, the carrier density markedly decreased from 8.4 x 10(18)/cm(3) to 9.9 x 10(16)/cm(3 )as the process pressure increased. Meanwhile, the electron mobility only slightly decreased from 11.9 cm(2)/V.s to 8.0 cm(2)/V.s. Inverted staggered IGZO-TFTs were fabricated. The switch characteristic of the TFTs can be effectively modulated by the pressure during the preparation of IGZO channel.