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We investigated the effects of ultraviolet (UV) light illumination on nitrogen-doped atomic layer deposited (ALD)-ZnO:N thin film transistors (TFTs). ALD ZnO:N thin films grown at 125°C were used as active layers for back-gate TFT devices. As-fabricated ALD ZnO:N TFTs showed proper drain current modulation response to a gate voltage sweep with a 5.4 V threshold voltage and a clear pinch-off. However, the threshold voltage was significantly shifted in the negative direction by UV exposure due to an associated increase in carrier concentration, resulting in the loss of current modulation by gate voltage sweep. In addition, we observed a resistivity change in ALD ZnO:N thin films with time after UV exposure. The resistivity decreased by several orders of magnitude upon UV light exposure and recovered toward its original value after switching off the UV light. Accordingly, the transfer curves of TFT devices using a ZnO:N active layer also exhibited recovery characteristics. We formed a thin Al2O3 passivation layer on top of the TFT surface in order to suppress the recovery effect. [ABSTRACT FROM AUTHOR]

The electrical properties of atomic layer deposition (ALD) nitrogen-doped ZnO (ZnO:N) thin films were investigated as a function of incorporated nitrogen concentration. The nitrogen concentrations in the films were controlled by using different concentrations of NH4OH solution, which was used as a single source for the reactant and nitrogen doping for ALD ZnO:N. The carrier concentrations in ALD ZnO:N decreased down to 6.13 X 1013/cm3 using 29% NH4OH solution. Thin film transistors (TFTs) were fabricated using ALD ZnO:N thin films with different N contents as active channel layers. The device properties were significantly changed by the amount of nitrogen incorporation due to the change in the electrical properties of ZnO:N films. Especially, threshold voltages were changed from 20.0 to 3.1 V by adjusting nitrogen doping. Additionally, dc bias stability was enhanced by the increment in nitrogen concentration, producing a robust TET at high nitrogen incorporation. Finally, a high performance flexible TET was fabricated using ALD ZnO:N as an active layer on poly(ethylene naphthalate) substrate. [ABSTRACT FROM AUTHOR]

Atomic layer deposition (ALD) process for oxynitrides of high-k gate dielectrics employing NH4OH as a single source for reactants, water and NH3, was studied. By this method, nitrogen was incorporated up to 1–3 at. % for ALD Al2O3 and Ta2O5 films from metal organic precursors. A comparative study with water based ALD showed that the electrical properties were improved. The leakage current of oxide films from NH4OH based ALD had been reduced and, more importantly, the dielectric strength was found to be enhanced by more than two orders of magnitude from a time dependent dielectric breakdown measurement. [ABSTRACT FROM AUTHOR]