Characteristics of Facing Target-Sputtered Amorphous InGaZnO Thin Films as the Active Channel Layer in Transparent Thin Film Transistor on Polymeric Substrate

For an application to the channel layer in flexible transparent thin-film transistor (TFT), we have prepared the amorphous indium gallium zinc oxide (a-InGaZnO) thin films on unheated polyethylene naphthalate (PEN) substrate by facing target sputtering. Two types of a-InGaZnO TFT design, one top gate configuration and the other bottom gate, have been fabricated for comparison with each other. The experimental results reveal that the top gate a-InGaZnO TFT is shown to be superior TFT performances, compared with bottom-gate structure. As a result, the top gate a-InGaZnO TFTs operate in depletion mode with a threshold voltage of −0.5 V, a mobility of 6.0 cm2/Vs, an on-off ratio of >106, and a sub-threshold slope of 0.95 V/decade. In addition, the optical transmittance of about 74% at 550nm wavelength is represented for the top gate a-InGaZnO TFT on PEN.

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