Abstract
We report the impact of yttrium oxide (YOx) passivation on the zinc oxide (ZnO) thin film transistor (TFT) based on Al2O3 gate insulator (GI). The YOx and ZnO films are both deposited by spray pyrolysis at 400 and 350 °C, respectively. The YOx passivated ZnO TFT exhibits high device performance of field effect mobility (μFE) of 35.36 cm2/Vs, threshold voltage (VTH) of 0.49 V and subthreshold swing (SS) of 128.4 mV/dec. The ZnO TFT also exhibits excellent device stabilities, such as negligible threshold voltage shift (∆VTH) of 0.15 V under positive bias temperature stress and zero hysteresis voltage (VH) of ~0 V. YOx protects the channel layer from moisture absorption. On the other hand, the unpassivated ZnO TFT with Al2O3 GI showed inferior bias stability with a high SS when compared to the passivated one. It is found by XPS that Y diffuses into the GI interface, which can reduce the interfacial defects and eliminate the hysteresis of the transfer curve. The improvement of the stability is mainly due to the diffusion of Y into ZnO as well as the ZnO/Al2O3 interface.
Highlights
The demand for low voltage and high-performance thin-film transistors (TFTs) for next-generation displays encourages the research towards oxide semiconductor
Metal oxides are favorable semiconductor for substituting amorphous Si and low temperature poly-Si (LTPS) for display applications, when high transparency is required in visible range [1,2,3]
We study the effect of yttrium oxide (Y2O3) passivation layer on the performance of zinc oxide (ZnO) TFT while using Al2O3 as a gate insulator
Summary
The demand for low voltage and high-performance thin-film transistors (TFTs) for next-generation displays encourages the research towards oxide semiconductor. Several techniques are used to deposit ZnO thin film such as sputtering, chemical vapor deposition, pulsed laser deposition, spin coating, and spray pyrolysis [6,7,8,9,10,11,12]. The hysteresis of the solution processed ZnO TFT on Al2O3 (high-k dielectric) is due to the oxygen related defects at the interface [14,15,16]. We study the effect of yttrium oxide (Y2O3) passivation layer on the performance of ZnO TFT while using Al2O3 as a gate insulator. Inter-diffusion of Yttrium (Y) into bulk ZnO and ZnO/Al2O3 interface can reduce the oxygen related defects This improves the bias stability of ZnO TFT
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