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We investigated the microstructure and electrical properties of Cu and Cu-Mn alloy on amorphous In-Ga-Zn-O (a-IGZO) oxide semiconductor in order to explore a high performance electrode material for thin film transistors (TFTs) in advanced flat panel displays. Current-voltage measurements of metal/semiconductor contact structure showed a non-linear behavior with Cu, while a good ohmic behavior [q C ¼ (1.2À2.9) Â 10 À4 XÁcm 2 ] with the Cu-Mn alloy after annealing at 250 C for 1 h. Transfer and output characteristics of TFT structure also showed excellent performance with the Cu-Mn alloy. The good electrical property was due to the formation of a highly doped n þ a-IGZO layer with the carrier density of 1.4 Â 10 20 cm À3 . The donor doping could be achieved simply by heat treatment to promote the oxidation of Mn and the reduction of a-IGZO.

We investigated the lateral distribution of the equilibrium carrier concentration ( n 0 ) along the channel and the effects of channel length ( L ) on the source-drain series resistance ( R ext ) in the top-gate self-aligned (TG-SA) coplanar structure amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs). The lateral distribution of n 0 across the channel was extracted using the paired gate-to-source voltage ( V GS )-based transmission line method and the temperature-dependent transfer characteristics obtained from the TFTs with different L s. n 0 abruptly decreased with an increase in the distance from the channel edge near the source/drain junctions; however, much smaller gradient of n 0 was observed in the region near the middle of the channel. The effect of L on the R ext in the TG-SA coplanar a-IGZO TFT was investigated by applying the drain current-conductance method to the TFTs with various L s. The increase of R ext was clearly observed with an increase in L especially at low V GS s, which was possibly attributed to the enhanced carrier diffusion near the source/drain junctions due to the larger gradient of the carrier concentration in the longer channel devices. Because the lateral carrier diffusion and the relatively high R ext are the critical issues in the TG-SA coplanar structure-based oxide TFTs, the results in this work are expected to be useful in further improving the electrical performance and uniformity of the TG-SA coplanar structure oxide TFTs.