Interdielectric Layer Engineering for Reliable Monolithic Integration of ITZO TFT Backplanes and InP QLEDs

초록

The electrical performance and driving capability of monolithically integrated oxide thin-film transistor (TFT)-quantum-dot light-emitting diode (QLED) pixels are strongly affected by the dielectric environment formed during backplane-emitter integration. In this study, three interdielectric configurations-single-layer Al2O3, single-layer SiO2, and an Al2O3/SiO2 bilayer-were systematically investigated to elucidate the influence of dielectric composition and interfacial chemistry on the stability of indium-tin-zinc oxide (ITZO) TFTs and QLED driving behavior. Although the Al2O3-only device exhibited the best intrinsic TFT performance, hydrogen diffused into the Al2O3/SiO2 bilayer during the plasma-enhanced chemical vapor deposition of SiO2, which generated donor-like defects in the ITZO channel and negatively shifted the threshold voltage. Nevertheless, the bilayer simultaneously provided superior current leakage suppression and compatibility with the subsequent solution-processed QLED fabrication, enabling stable pixel operation. The bilayer-based TFT achieved a mobility of 24.82 cm(2) V-1 s(-1), a subthreshold swing of 0.09 V dec(-1), and an on/off ratio of 8.78 x 10(9). When used to drive InP QLEDs, the integrated pixel reached a peak luminance of 9,488.8 cd m(-2), a maximum current density of 285.3 mA cm(-2), and an external quantum efficiency of 7.15%, while maintaining an unchanged electroluminescence spectrum when driven by TFTs. These results demonstrate that interdielectric layer engineering, particularly the balance between hydrogen-induced voltage threshold shifts and process robustness, is critical for achieving reliable monolithic TFT-QLED operation for next-generation active-matrix display technologies.

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