Robust Growth of Atomically Thin Ternary Transition Metal Dichalcogenide Heterophase Homojunctions for Enhanced Photodetection Performance

ABSTRACT The tunable phase structure of atomically thin transition metal dichalcogenides (TMDs) offers a high flexibility to tailor their band structures and carrier dynamics for integrated photonic and optoelectronic devices. However, synthesizing highly crystalline hetero-phase TMD homojunctions with high carrier lifetime—a key requirement for high-performance photodetectors—remains a significant challenge to date. Here we report computationally guided robust growth of monolayer ternary MoSe 2(1- x ) Te 2 x heterophase homojunctions via a composition-driven phase transition strategy. Density-functional theory calculations reveal that the polymorphic phase structures of MoSe 2(1- x ) Te 2 x alloys stem from a delicate competition of thermodynamic stability between semiconducting 2H phase and semi-metallic 1T' phase. The Te/Se alloying strategy expands the growth window of 2H/1T' mixed phase, leading to a robust growth of high-quality monolayer MoSe 2(1- x ) Te 2 x heterophase homojunctions. Benefiting from continuous band bending and highly efficient separation of photocarriers at MoSe 2(1- x ) Te 2 x heterophase interface, the fabricated photodetectors exhibit broadband response from visible to near-infrared light, high on-off ratio up to 2.8×10 4 , and high peak responsivity of 7.02 A/W with a specific detectivity of 6.1×10 13 Jones at room temperature, which are far superior to the state-of-the-art single-phase TMD devices. Moreover, the photodetector has been also demonstrated for the high-resolution visible-to-near infrared imaging and multi-band encrypted communication, verifying its huge potential for practical applications. This work provides an efficient route to prepare high-quality monolayer TMD heterophase homojunctions as a scalable paradigm for integrated optoelectronic devices.