Enhanced Stability in Zr-Doped ZnO TFTs With Minor Influence on Mobility by Atomic Layer Deposition

Abstract

We developed a novel method to fabricate Zr-doped ZnO (ZrZnO) thin films via low-temperature atomic layer deposition technique. ZrZnO films were deposited by diethylzinc (DEZ)/tetrakiszirconium (TDMAZr)/H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O cycles instead of the traditional DEZ/H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O/TDMAZr/H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O cycles and applied in thin-film transistors (TFTs). It is found that ZrZnO-TFTs with a Zn-Zr-O:ZnO atomic ratio of 1:49, i.e., ZrZnO (1:49) exhibit excellent properties, such as a minimum subthreshold swing value of 0.37 V/dec, a maximum ION/IOFF value of 2.4 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sup> , a larger mobility of 12.38 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /V·s, and a smaller threshold voltage shift (ΔVth) of 0.61 V under temperature stress from 25 °C to 105 °C, which are superior compared with TFTs with ZnO channel doped by ZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> layer. The stability of ZnO TFTs was improved greatly by Zr-Zn-O doping. Moreover, the field-effect mobility of ZrZnO-TFTs was rarely influenced. Temperature-stress test was carried out to build up the correlation model in terms of the defect structures, subgap states, and stability. These results could provide a new access to understand the device instability of ZrZnO TFTs.