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[International Journal] Suppressed instability of a-IGZO Thin Film Transistors under negative bias illumination stress using the Distributed Bragg Reflectors
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Eungtaek Kim, Woo Jae Jang, Woohyun Kim, Junhong Park, Myung Keun Lee, Sang-Hee K. Park and Kyung Cheol Choi

IEEE Transactions on Electron Devices , March , 2016

Published

vol 63, no 3, pp 1066-1071

Abstract
We suggest functional passivation layers in the form of a distributed Bragg reflector (DBR) composed of ZnS and LiF for transparent thin-film transistors (TFTs) to improve the stability under negative bias illumination stress (NBIS). The luminous transmittance of the DBR was 82.0% when the number of dyads was 3.5, and the thicknesses of ZnS and LiF
were 42 and 85 nm, respectively. We applied the DBR to TFTs based on amorphous indium-gallium-zinc oxide without the degradation of electrical performance, such as the mobility,
ON–OFF ratio, subthreshold swing, and VON. The luminous transmittance of the TFT with the DBR was measured as 71.6%. VON of the TFT with the DBR was reduced to −1.119 V
compared with that of the reference TFT, which is −3.261 V when a 1.25 MV/cm electric field was applied, and white light was illuminated during 3000 s. This confirms that the functional
passivation layers suggested, in this paper, provide a solution to suppress the instability of TFTs in the NBIS and enhance the optical transmittance of transparent displays.