Electrical defect passivation of nanocrystalline In-Ga-O thin film transistor with organic-inorganic superlattice structure

초록

Metal oxide thin film transistors have received tremendous attention due to various advantages over the conventional Si-based TFT for the next-generation wearable electronics. However, the surface of a metal oxide thin film is very sensitive to ambient molecules such as moisture and oxygen, degrading the device performance after long-term operation. In this work, we report on utilizing the passivation effect from various phosphonic acids (PAs) to suppress the adsorption of ambient chemical species and the oxygen vacancy defect in the superlattice (SL) structure prepared by insertion of PA between two nanocrystalline In-Ga-O (nc-IGO) layers (7.5% atomic percentage). The most effective stabilization of SL structure is successfully realized with 1,10-decyl diphosphonic acid (P10) treatment. Very impressively, the reference device with pristine nc-IGO film around 10 nm shows a large threshold voltage (V-th) shift of 11.80 V after 10,000 s of PBS (V-G = 50 V, V-DS = 25 V), but the optimized device with P10 SL structure with similar thickness shows a negligible V-th of 1.21 V with same stress condition. Furthermore, the oxygen vacancy defect suppression also resulted in a small V-th shift of 2.94 V after 10,000 s NBS (V-G = -50 V, V-DS = -25 V).

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