Observation of 1/f ⁴ Noise in Organic Bilayer Ambipolar FETs and Proposition of Defect Engineering Method for Ultimate Noise Control

The omnipresence of low-frequency noise (LFN) within semiconductor materials and devices poses a substantial concern for the reliability of integrated circuits (ICs). Consequently, considerable research endeavors are directed toward characterizing LFN across various types of field-effect transistors (FETs), pivotal components in IC. Here, the LFN characteristics of bilayer ambipolar FETs based on organic semiconductors are investigated, / uri / We report that interface defects at the n/p junctions engender a correlation between trapping/detrapping noise and generation/recombination noise, resulting in a 1/f ⁴ noise. The elucidation of this distinctive noise behavior is conducted through comprehensive and comparative studies on LFN of single n- and p-channel FETs. Furthermore, a novel approach is proposed to control excess noise in bilayer ambipolar FETs by inserting a thin insulator layer (parylene) between the n/p junction. This yields a notable reduction in noise amplitude, concurrently leading to the dissolution of 1/f ⁴ noise into 1/f ³ and 1/f ² components. This study not only furnishes the inaugural report of the underlying mechanism behind the unique 1/f ⁴ noise but also presents a pragmatic strategy for its control, thereby opening a new horizon for LFN studies on organic-based FETs.