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

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
²
/Vs in comparison to earlier reported values of 0.1-0.7 cm
²
/Vs for ZnO TFTs while maintaining desired threshold voltages of 1-2 V and I
_ON
/I
_OFF
ratios of 10
⁷
-10
⁹
.