Low-voltage, high-performance polymeric field-effect transistors based on self-assembled monolayer-passivated HfOx dielectrics: Correlation between trap density, carrier mobility, and operation voltage

Abstract

We report on high-performance polymeric field-effect transistors (PFETs) operating at low voltages ( V op ) using a self-assembled monolayer (SAM)-passivated HfO x dielectric layer. A diketopyrrolopyrrole and quaterthiophene-based copolymer (PDPP2DT-T2) was spin-coated in air as an active channel material on top of a HfO x gate dielectric that was passivated with n -octyltrichlorosilane (OTS), n -octadecyltrichlorosilane (ODTS), and n -dodecylphosphonic acid (PAC12) SAMs. The high capacitance and low leakage current of the SAM-passivated HfO x dielectrics enabled the devices to operate at | V op | of less than 4 V. In particular, the PFETs using ODTS-passivated HfO x demonstrated a high hole mobility ( μ eff h ) of 1.98 cm 2 V −1 s −1 , a current on/off ratio of 1.4 × 10 4 , and a threshold voltage of −0.8 V despite the fact that the device fabrication and all measurements were conducted under ambient conditions without encapsulation. Moreover, the μ eff h value observed in this study is the best for high- k -dielectric-based low-voltage PFETs reported to date. This work demonstrates that our facile modification of high- k dielectrics with SAMs is a highly effective method for realizing high-performance semiconducting copolymer-based transistors working at a low V op regime with low power consumption. • High-performance PFETs are demonstrated using a self-assembled monolayer-passivated HfO x dielectric layer. • The HfO x layer was passivated with n -octyltrichlorosilane, n -octadecyltrichlorosilane, and n -dodecylphosphonic acid. • The high capacitance of the SAM-passivated HfO x dielectrics enabled the devices to operate at .| V op | of < 4 V. • The PFETs using ODTS/HfO x demonstrated a high hole mobility of 1.98 cm 2 V −1 s −1 and a threshold voltage of −0.8 V.