Improved high voltage operation of amorphous In-Ga-Zn-O thin film transistor by carrier density enhancement.
HyoungBeen JuJiyoung BangHyeonjeong SunYeunghun LeeSangduk KimSeungmin ChoiYoungsoo NohHyo Won KimEunsuk ChoiJae Kyeong JeongSeung-Beck LeePublished in: Nanotechnology (2024)
We report on improved high voltage operation of amorphous-In-Ga-Zn-O (a-IGZO) thin film transistors (TFTs) by 
increasing carrier density and distributing the high bias field over the length of the device which utilizes an off-set drain 
structure. By decreasing the O2 partial pressure during sputter deposition of IGZO, the channel carrier density of the high 
voltage a-IGZO TFT (HiVIT) was increased to ~1018 cm-3. Which reduced channel resistance and therefore the voltage drop 
in the ungated offset region during the on-state. To further decrease the electric field in the offset region, we applied Ta 
capping and subsequent oxidation to locally increase the oxygen vacancy levels in the offset region thereby increasing local 
carrier density. The reduction of the drain field in the offset region from 1.90 V/μm to 1.46 V/μm at 200 V drain voltage, 
significantly improved the operational stability of the device by reducing high field degradation. At an extreme drain voltage of 500 V, 
the device showed an off-state current of ~10-11 A and on-state current of ~1.59 mA demonstrating that with further 
enhancements the HiVIT may be applicable to thin-film form, low leakage, high voltage control applications.
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