Complementary Doping Strategy for Achieving Low Contact-Resistance in p-Type Two-Dimensional Field-Effect Transistors

Lowering contact resistance (<i>R</i>_C) is essential for achieving high-performance complementary logic circuits based on two-dimensional (2D) field-effect transistors (FETs). Although n-type 2D FETs have reached sub-100 Ω·μm <i>R</i>_C, attaining a similar performance in p-type devices remains difficult due to large Schottky barriers for hole injection. We present a strategy to reduce <i>R</i>_C in p-type monolayer WSe₂ FETs to the sub-kΩ·μm range by combining complementary doping with a clean 2D/2D van der Waals (vdW) interface. Degenerately Ta-doped multilayer MoSe₂ acts as a robust p-type contact and is laminated onto the MOCVD-grown WSe₂ channels. A postfabrication NO anneal induces selective channel doping through NO chemisorption at Se-vacancy sites while preserving the Ta-doped MoSe₂ contact properties. This combined channel and contact engineering enable efficient hole injection, yielding <i>I</i>_ON values up to 53 μA/μm. The approach narrows the performance gap between n- and p-type 2D transistors and advances the prospects for complementary 2D logic technologies.