Centimeter-Scale Two-Phase Mixed Re _0.58 Mo _0.42 S ₂ Grown via Low-Pressure Chemical Vapor Deposition and Its Heterostructure with GaSe for High-Performance Photodetectors

Two-dimensional (2D) Re x Mo 1– x S 2 ternary transition-metal dichalcogenides are attracting increasing attention because their bandgap and conductivity are tunable, and their conductivity type can be switched from n-type to p-type through phase engineering, enabling applications in photodetection and photocatalysis. However, a high density of grain boundaries in 2D Re x Mo 1– x S 2 films strongly scatters carriers and degrades the photodetector performance. Here, we address this limitation by constructing a Re 0.58 Mo 0.42 S 2 /GaSe heterostructure, in which exfoliated 2D GaSe flakes, as a high-quality carrier transport layer, are dry-transferred and inserted between Re 0.58 Mo 0.42 S 2 and the metal electrodes. Re 0.58 Mo 0.42 S 2 with a thickness of 2.5 nm and a lateral size up to 1 cm was grown on mica by low-pressure chemical vapor deposition (LPCVD). The film exhibits a mixed crystal structure of 1T’ and 2H phases, which are p-type and n-type, respectively. The 1T’/2H interface forms a p–n junction that promotes separation of photogenerated carriers, while the band alignment in the heterostructure drives hole transfer to GaSe, thereby improving carrier separation and transport. The Re 0.58 Mo 0.42 S 2 /GaSe photodetector achieves a responsivity ( R ) of 840 A/W, an external quantum efficiency (EQE) of 2.32 × 10 5 %, a specific detectivity ( D *) of 1.10 × 10 10 Jones, and a rise/decay time of 3 ms/1 ms, outperforming devices based solely on Re 0.58 Mo 0.42 S 2 or GaSe. These results demonstrate that heterostructures based on two-phase mixed ternary semiconductors are promising for high-performance photodetection.