Effect of Channel Length on the Reliability of Amorphous Indium--Gallium--Zinc Oxide Thin Film Transistors

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We investigated the effect of the channel length on the reliability of amorphous indium--gallium--zinc oxide (IGZO) thin-film transistors (TFTs) under the negative and positive gate bias stress. The threshold voltage (V_{\text{th}}) was barely changed at the channel length of 8 μm under the negative bias stress. When the channel length was 10 and 15 μm, V_{\text{th}} shifted negatively about 0.7 and 2.5 V. However, V_{\text{th}} shift did not depend on the channel length under the positive bias stress. Under the negative gate bias stress, the holes might not be accumulated uniformly at the channel. Because the band gap of IGZO is large, the effect of negative gate bias is decreased when the back interface is fixed by source/drain electrode. When the channel length decreases, the amount of accumulated hole decreases and V_{\text{th}} shift decreases.
2012-03-25