3 years ago

Enhanced Light Stability of InGaZnO Thin-Film Transistors by Atomic-Layer-Deposited Y2O3 with Ozone

Enhanced
Light Stability of InGaZnO Thin-Film Transistors by Atomic-Layer-Deposited
Y2O3 with Ozone
Bo-Eun Park, Woo-Hee Kim, Yun Cheol Kim, Su Jeong Lee, Hyungjun Kim, Satoko Gatineau, Whang Je Woo, Jae-Min Myoung, Il-Kwon Oh, Hanearl Jung, Christian Dussarrat
We report the effect of Y2O3 passivation by atomic layer deposition (ALD) using various oxidants, such as H2O, O2 plasma, and O3, on In–Ga–Zn–O thin-film transistors (IGZO TFTs). A large negative shift in the threshold voltage (Vth) was observed in the case of the TFT subjected to the H2O-ALD Y2O3 process; this shift was caused by a donor effect of negatively charged chemisorbed H2O molecules. In addition, degradation of the IGZO TFT device performance after the O2 plasma-ALD Y2O3 process (field-effect mobility (μ) = 8.7 cm2/(V·s), subthreshold swing (SS) = 0.77 V/dec, and Vth = 3.7 V) was observed, which was attributed to plasma damage on the IGZO surface adversely affecting the stability of the TFT under light illumination. In contrast, the O3-ALD Y2O3 process led to enhanced device stability under light illumination (ΔVth = −1 V after 3 h of illumination) by passivating the subgap defect states in the IGZO surface region. In addition, TFTs with a thicker IGZO film (55 nm, which was the optimum thickness under the current investigation) showed more stable device performance than TFTs with a thinner IGZO film (30 nm) (ΔVth = −0.4 V after 3 h of light illumination) by triggering the recombination of holes diffusing from the IGZO surface to the insulator–channel interface. Therefore, we envisioned that the O3-ALD Y2O3 passivation layer suggested in this paper can improve the photostability of TFTs under light illumination.

Publisher URL: http://dx.doi.org/10.1021/acsami.7b14260

DOI: 10.1021/acsami.7b14260

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