High-Performance UV Detector Using Al-Doped ZnO Phototransistor Prepared by Initiated-CVD Doping Technique

A novel doping technique with an initiated chemical vapor deposition (iCVD) process is applied to fabricate aluminum (Al)-doped zinc oxide (ZnO) channel thin-film ultraviolet (UV) phototransistor (PT). The iCVD doping technique can successfully introduce Al throughout the ZnO channel without any surface damage. The sub-bandgap states mainly due to oxygen vacancy (VO) defects in the ZnO channel are effectively suppressed by Al doping; the subthreshold swing (SS) of the PT has been reduced by more than half to 168 mV/dec and under negative gate bias illumination stress, the threshold voltage shift is reduced by about half to −2.03 V, which improves the reliability. For the UV detection, the Al-doped ZnO PT exhibits a high responsivity of 358.93 A<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula> W−1, an ultrahigh UV-to-visible rejection ratio of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4.81\times 10^{{6}}$ </tex-math></inline-formula>, a high detectivity (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${D} ^{\ast } $ </tex-math></inline-formula>) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.68\times 10^{{15}}$ </tex-math></inline-formula> Jones, a low noise equivalent power (NEP) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.98\times 10^{-{18}}$ </tex-math></inline-formula> W<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula> Hz−1, and fast switching performance. The developed Al-doped ZnO PT can be used in low-cost and high-performed UV detection for various applications.