Fabrication and investigation of the electrical performance of nitrogenated bilayer ZnO:N/ZnO thin-film transistors

In this study, a bilayer ZnO:N/ZnO thin-film transistors (TFTs) was designed to improve both the performance and stability of single-layer ZnO TFTs, using the effects of N-treatment on oxygen vacancy (VO) and the interface trap density. Bilayer ZnO:N/ZnO films and related TFTs were fabricated via radiofrequency magnetron sputtering in a mixture of Ar and N2 gas at 150°C. The electrical performance and bias-stress stability were systematically investigated. The bilayer ZnO:N/ZnO TFT exhibited a linear field-effect mobility of 13.6 cm2/Vs, high current on-to-off ratio (Ion/Ioff) of 1 × 107, small threshold voltage (Vth) of 2.6 V, and low subthreshold swing of 0.32 V/decade compared with single-layer undoped ZnO and ZnO:N TFTs. Moreover, ZnO:N/ZnO TFT exhibited small threshold voltage shifts (∆Vth) of 0.8 and –0.9 V according to positive bias illumination stress and negative bias illumination stress measurements, respectively. X-ray photoelectron spectroscopy analysis showed that the N-treatment passivated the VO defects, reduced the density of interface traps, and controlled the carrier concentration. Thus, the performance and stability of the ZnO:N/ZnO TFTs were improved. Therefore, ZnO:N/ZnO TFTs have good application prospects in transparent thin-film electronics and flat-panel displays.