Direct Synthesis and Enhanced Rectification of Alloy-to-Alloy 2D Type-II MoS2(1-x)Se2x/SnS2(1-y)Se2y Heterostructures

The interfacial tunable band alignment of heterostructures is coveted in device design and optimization of device performance. As an intentional approach, alloying allows band engineering and continuous band-edge tunability for low-dimensional semiconductors. Thus, combining the tunability of alloying with the band structure of a heterostructure is highly desirable for the improvement of device characteristics. In this work, the single-step growth of alloy-to-alloy (MoS2(1-x)Se2x/SnS2(1-y)Se2y) 2D vertical heterostructures is demonstrated. Electron diffraction reveals the well-aligned heteroepitaxial relationship for the heterostructure, and a near-atomically sharp and defect-free boundary along the interface is observed. The nearly intrinsic van der Waals (vdW) interface enables measurement of the intrinsic behaviors of the heterostructures. The optimized type-II band alignment for the MoS2(1-x)Se2x/SnS2(1-y)Se2y heterostructure, along with the large band offset and effective charge transfer, is confirmed through quenched PL spectroscopy combined with density functional theory calculations. Devices based on completely stacked heterostructures show one or two orders enhanced electron mobility and rectification ratio than those of the constituent materials. The realization of device-quality alloy-to-alloy heterostructures provides a new material platform for precisely tuning band alignment and optimizing device applications.

Automated summary

The study demonstrates the single-step growth of MoS2(1-x)Se2x/SnS2(1-y)Se2y 2D alloy-to-alloy vertical heterostructures with well-aligned heteroepitaxial relationship and optimized type-II band alignment, leading to significantly enhanced device performance in terms of electron mobility and rectification ratio.