Instability of threshold voltage under constant bias stress in pentacene thin film transistors employing polyvinylphenol gate dielectric

Abstract

The instability of threshold voltage and mobility of pentacene thin film transistors using a poly(4-vinylphenol) gate dielectric have been investigated under constant bias stress. The mobility was very stable in vacuum by exhibiting 2% variation after 6 h stress even under the high gate bias stress of V GS = − 20 V. Meanwhile, we observe a negative shift of threshold voltage under stress in vacuum. This shift is attributed to charges trapped in deep electronic states in pentacene near the gate interface. We propose a model for the negative shift of the threshold voltage and extract the hole concentration, 4.5 × 10 11 cm − 2 , needed to avoid the onset of stress effects, resulting in a design rule of the channel width to length ratio larger than 40.