Epitaxial Integration of Er‐Doped WSe ₂ Monolayer on Silicon for High‐Performance Photodetectors

ABSTRACT Direct growth of single‐crystalline two‐dimensional (2D) semiconductors on silicon substrates offers high silicon compatibility and enables the fabrication of clean heterointerfaces. However, this approach is typically challenged by intrinsically weak interfacial interactions and unregulated chemical reactions at the heterointerface. Herein, we demonstrate a one‐step chemical vapor deposition (CVD) epitaxial integration strategy that enables the in‐situ growth of single‐crystalline erbium‐doped tungsten selenide (WSe ₂ ) on silicon‐on‐insulator (SOI) substrates through SOI substrate pretreatment combined with the optimization of growth temperature and atmosphere. Through this strategy, we successfully fabricated erbium‐doped WSe ₂ with a maximum single‐crystal size of 300 µm and a thickness of 1.15 nm. Simultaneously, large‐area growth and high‐concentration erbium ion (Er ³⁺ ) doping were achieved, allowing the direct construction of a clean erbium‐doped WSe ₂ /Si van der Waals heterojunction without any transfer processes. The photodetector fabricated using this heterojunction demonstrates excellent performance. Under 635 nm light illumination, it achieves a responsivity as high as 30.58 A/W, an external quantum efficiency (EQE) of 5983.9%, and a specific detectivity (D*) of 6.84 × 10 ¹² Jones. Compared with undoped devices, the metrics are enhanced by more than 34 times. This transfer‐free route provides a promising platform for high‐sensitivity optoelectronic devices in imaging, sensing, and on‐chip photonics.