h-BN-assisted Metal Contact Transfer to InSe for Two-Dimensional Multifunctional Electronic Devices

Abstract Metal contacts to two-dimensional (2D) semiconductors are crucial for determining the electrical performance of electronic devices. However, traditional three-dimensional metal deposition processes cause damage to 2D semiconductors and considerable Fermi-level-pinning effects. In this study, a hexagonal boron nitride (h-BN)-assisted transfer method was proposed for transferring metal contacts to few-layered InSe for fabricating 2D functional electronic devices. Using the transferred Pt electrodes as the contact, p-type dominated ambipolar conduction behavior with the hole Schottky barrier height (SBH) approaching 0 meV was observed in field-effect transistors (FETs) comprising multilayered InSe. Based on this phenomenon, several InSe homojunctions were fabricated using a dual-gate modulating method such as p–p, n–n, p–n, and n–p. For InSe p–n homojunctions, a current rectification ratio of over 10⁴ and optoelectronic detection capabilities were achieved. Furthermore, a complementary metal–oxide–semiconductor (CMOS) inverter with an ultra-high voltage gain exceeding 60 at V_DD = −1 V was fabricated. The proposed h-BN-assisted metal contact transfer method can be easily extended to other 2D semiconductors for fabricating complementary electronic and optoelectronic devices.