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 (Vop) using a self-assembled monolayer (SAM)-passivated HfOx dielectric layer. A diketopyrrolopyrrole and quaterthiophene-based copolymer (PDPP2DT-T2) was spin-coated in air as an active channel material on top of a HfOx 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 HfOx dielectrics enabled the devices to operate at |Vop| of less than 4 V. In particular, the PFETs using ODTS-passivated HfOx demonstrated a high hole mobility (μeff h) of 1.98 cm2 V−1 s−1, a current on/off ratio of 1.4 × 104, 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 μeff 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 Vop regime with low power consumption.