High-Performance ALD Al-Doped ZnO Thin-Film Transistors Grown on Flexible Substrates

Abstract

We report a CMOS compatible high-performance ALD Al-doped ZnO thin-film transistor (TFT) fabricated on flexible substrate with a sub-150 °C processing temperature. The TFTs channel are optimized through Al doping (2-3 at.%) using all low-temperature steps to enable flexible substrate processing while minimizing the piezoelectric effect in the channel. The optimized device has an electron mobility as high as ~30 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /Vs in comparison to earlier reported values of 0.1-0.7 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /Vs for ZnO TFTs while maintaining desired threshold voltages of 1-2 V and I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> /I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OFF</sub> ratios of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> -10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9</sup> .