Bilayer channel structure to improve the stability of solution-processed metal oxide transistors under AC stress

초록

In this work, we report solution-processed bilayer channel thin film transistors (TFTs) based on solutionprocessed amorphous oxide semiconductors (AOSs) that fulfill both superb electrical performance and device stability against applied alternating current (AC) drain bias stress. Acceptor-like states generation via hot carrier effect (HCE) is a representative device degradation mechanism suggested for AOS-based TFTs when subjected to AC bias stress, featuring threshold voltage (Vth) shift and on-current (Ion) lowering. As excess electric field and accumulated carriers in the AOS channel cause HCE, alleviating carrier accumulation is a key solution for mitigating HCE. Bilayer channel TFTs comprising two different AOSs could work as a countermeasure to overcome HCE since proper energy band alignment of two channels creates a conduction band difference that act as the energy barrier for carriers. In this regard, we employed amorphous indium-gallium-zinc oxide (IGZO) and zinc-tin oxide (ZTO) as bottom and top layer, respectively, for bilayer channel TFT. Designed bilayer channel showed a conduction band difference of 0.18 eV, and fabricated TFT based on this architecture exhibited high mobility over to 5.9 cm2/Vs with slight Vth shift of 0.1 V and Ion lowering of 1.7% for 1000 s against applied AC stress, demonstrating device stability under AC drain bias stress.

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