Electrochemical Anodization for the Fabrication of Wafer‐Scale p‐Type Organic Permeable Base Transistors Arrays with MHz Operation

Organic thin-film transistors (OTFTs) are promising for flexible, low-cost, and biocompatible electronics. However, conventional planar OTFTs are hindered by the large channel length limiting the transconductance and switching frequencies. Vertical OTFTs, particularly organic permeable-base transistors (OPBTs), address these challenges with short channel lengths defined by the layer thickness. While n-type OPBTs have advanced significantly, p-type OPBTs face challenges such as lower transmission, higher leakage currents, and unreliable fabrication processes. This work introduces a wafer-scale method for fabricating p-type OPBTs using electrochemical anodization of the base electrode. The anodization process applied directly atop the organic semiconductor, preserves electrical properties while suppressing base leakage. The resulting anodized OPBTs exhibit high-performance characteristics, including an on-current density of 301 mAcm^-2, low leakage current of 4.32 × 10^-9 A, maximum transmission of 99.9999%, and a maximum current gain of 1.89 × 10⁶-a 100,000-fold improvement over prior methods. Small signal analysis reveals a cutoff frequency of 1.49 MHz, with a voltage-normalized cutoff frequency of 0.54 MHzV^-1. Large-scale arrays show 96.3% fabrication yield and excellent uniformity. Complementary inverters integrating n- and p-type OPBTs exhibit superior switching, highlighting the potential of anodized OPBTs for advanced applications in displays and circuits.