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

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)/H2O cycles instead of the traditional DEZ/H2O/TDMAZr/H2O 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 I-ON/I-OFF value of 2.4x 10(7), a largermobility of 12.38 cm(2)/V.s, and a smaller threshold voltage shift (Delta Vth) of 0.61 V under temperature stress from 25 degrees C to 105 degrees C, which are superior compared with TFTs with ZnO channel doped by ZrO2 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.