Transparent thin-film transistors with zinc indium oxide channel layer

High mobility, n-type transparent thin-film transistors (TTFTs) with a zinc indium oxide (ZIO) channel layer are reported. Such devices are highly transparent with similar to 85% optical transmission in the visible portion of the electromagnetic spectrum. ZIO TTFTs annealed at 600 degrees C operate in depletion-mode with threshold voltages -20 to -10 V and turn-on voltages similar to 3 V less than the threshold voltage. These devices have excellent drain current saturation, peak incremental channel mobilities of 45-55 cm(2) V-1 s(-1), drain current on-to-off ratios of similar to 10(6), and inverse subthreshold slopes of similar to 0.8 V/decade. In contrast, ZIO TTFTs annealed at 300 degrees C typically operate in enhancement-mode with threshold voltages of 0-10 V and turn-on voltages 1-2 V less than the threshold voltage. These 300 degrees C devices exhibit excellent drain-current saturation, peak incremental channel mobilities of 10-30 cm(2) V-1 s(-1), drain current on-to-off ratios of similar to 10(6), and inverse subthreshold slopes of similar to 0.3 V/decade. ZIO TTFTs with the channel layer deposited near room temperature are also demonstrated. X-ray diffraction analysis indicates the channel layers of ZIO TTFTs to be amorphous for annealing temperatures up to 500 degrees C and polycrystalline at 600 degrees C. Low temperature processed ZIO is an example of a class of high performance TTFT channel materials involving amorphous oxides composed of heavy-metal cations with (n-1)d(10)ns(0) (n >= 4) electronic configurations. (C) 2005 American Institute of Physics.