Passivation effect on gate-bias stress instability of carbon nanotube thin film transistors

Abstract

A prior requirement of any developed transistor for practical use is the stability test. Random network carbon nanotube-thin film transistor (CNT-TFT) was fabricated on SiO2/Si. Gate bias stress stability was investigated with various passivation layers of HfO2 and Al2O3. Compared to the threshold voltage shift without passivation layer, the measured values in the presence of passivation layers were reduced independent of gate bias polarity except HfO2 under positive gate bias stress (PGBS). Al2O3 capping layer was found to be the best passivation layer to prevent ambient gas adsorption, while gas adsorption on HfO2 layer was unavoidable, inducing surface charges to increase threshold voltage shift in particular for PGBS. This high performance in the gate bias stress test of CNT-TFT even superior to that of amorphous silicon opens potential applications to active TFT industry for soft electronics.