Enhancing the electrical performance and stability of Hf-doped InZnO thin film transistors using dual-target co-sputtering technique

In this study, hafnium (Hf) was doped into InZnO films and related thin-film transistors (TFTs) were fabricated using co-sputtering. The optimal concentration of Hf doping atoms was obtained by controlling the power of dual targets InZnO and HfO2 and comparing their performances with those of HfInZnO TFTs that were fabricated from a single target, thus achieving high-performance and highly stable HfInZnO TFTs. After optimization, high-performance HfInZnO (PIZO70W-PHfO250W) TFTs with μFE value of 26.1 cm2/V s, SS value of 0.251 V/dec., and Vth value of 0.7 V were obtained. The results of experimental characterization indicate that co-sputtering with Hf doping reduced the oxygen vacancies, surface defects, and other trap densities of the device. Moreover, the co-sputtering prepared HfInZnO TFT exhibited the highest stability for small Vth shifts of 0.8 (−0.9) and 1.2 (−1.6) V under the gate bias and light illumination stress tests. Furthermore, low-frequency noise measurements demonstrated that the optimal Hf doping concentration in the HfInZnO films was controlled by the dual-target co-sputtering method, resulting in a lower number of oxygen vacancies and a lower interface trap density of the devices, thus enhancing the stability of HfInZnO TFTs. Overall, HfInZnO TFTs prepared using dual-target co-sputtering are found to be useful for achieving high-performance oxide TFTs.