Mobility and stability improvements through in-situ AlOx passivation on extremely thin 2-nm-thick InOx back-gate FETs

Abstract The effectiveness of in-situ AlOx passivation on mobility and stability improvement in 2-nm-thick InOx FETs is comprehensively investigated at atomic layer deposition (ALD) temperature ranging from 100oC to 200oC. The chemical state of extremely thin InOx channels are significantly changed by the in-situ AlOx passivation. As a result, AlOx/InOx FETs show superior overdrive current and hysteresis characteristic than those of InOx FETs fabricated at the same ALD temperature. It is also found that a AlOx passivation layer formed at 200oC results in a stronger reduction of InOx, leading to a mobility enhancement of 1.8 against AlOx/InOx FET fabricated at 100oC thanks to an increase of oxygen vacancies and resultant enhanced hopping conduction. For bias stability analysis, amount of hydrogen-induced trapping site within both AlOx and InOx layer is reduced at a higher ALD temperature, resulting in the improvement of both positive and negative bias stress stability.