Low Temperature MOCVD Synthesis of High‐Mobility 2D InSe

ABSTRACT 2D indium selenide (InSe) is a layered semiconductor with high electron mobility and a tunable band gap ranging from 1.25 eV in the bulk to 2.8 eV in the monolayer limit. However, growing phase‐pure InSe remains challenging due to the complex indium–selenium (In–Se) phase diagram. This complexity and the sensitivity of chemical precursors to growth conditions make it difficult to control which In–Se phase forms during synthesis during, e.g., metal‐organic chemical vapor deposition (MOCVD). MOCVD is considered the most promising approach for growing InSe, as it enables wafer‐scale, uniform, and controllable deposition—key requirements for device integration. We present a systematic investigation of InSe synthesis on c‐plane sapphire substrates at low temperatures. By varying Se/In precursor ratio and growth temperature, we create a phase diagram that covers In‐rich, equal stoichiometric, and Se‐rich In x Se y phases. Raman spectroscopy and atomic force microscopy, supported by energy dispersive X‐ray spectroscopy and scanning transmission electron microscopy, reveal formation conditions of 2D InSe. The epitaxial alignment is verified by in‐plane X‐ray diffraction. Samples grown under optimized conditions exhibit a strong optical absorption in the visible range and especially a comparably high electron mobility, underlining the potential of the MOCVD‐grown material for future applications.