Vertical Electric Field-Induced Abnormal Capacitance–Voltage Electrical Characteristics in a-InGaZnO TFTs

Abstract

This study investigates an abnormal degradation induced in a moist environment. Although devices maintain optimal performance under bias stress operation in a vacuum, an abnormal hump is observed in capacitance-voltage (C- V) electrical characteristics under negative bias stress (NBS) operation in a moist environment. Electrolysis of the H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O model is proposed to explain the degradation. An asymmetric stress condition, with V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GD</sub> = 0 V, is designed to confirm that a vertical electric field causes the electrolysis of H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O, which is the reason for the hump phenomenon in the C-V curve. Moreover, COMSOL simulation and C- V measurement of the source and drain parasitic capacitances are utilized to clarify the precise degradation position and support the mechanism. The results from electrical measurement suggest that a vertical electric field can cause instability in a moist environment.