Superior P-Type Switching in InSe Nanosheets for Complementary Multifunctional Systems

van der Waals (vdW) indium selenide (InSe) is receiving attention for its exceptional electron mobility and moderate band gap, enabling various applications. However, the intrinsic n-type behavior of InSe has restricted its use predominantly to n-type devices, constraining its application in complementary integrated microsystems. Here, we show superior ambipolar InSe transistors with vdW bottom contacts, achieving impressive p-type on/off current ratios greater than 10⁹ and Schottky barrier heights approaching the ideal Schottky-Mott limit. By introducing a partially gate-coupled architecture, we also demonstrate an ambipolar-to-unipolar transition and reconfigurable complementary multifunctionality, including n-type and p-type transistors as well as negative and positive rectifiers and breakdown diodes. The rectification polarity and ratio are gate-tunable from 3.5 × 10⁷ down to ∼10 without complex heterostructures, chemical doping, and multigate layouts. The negative and positive breakdowns are reversible, with both the breakdown voltage and switching ratio, which can exceed 10⁸, also being electrically tunable.