Semiconductor Performance Optimization on Quasi-Two-Dimensional Bi₂O₂(S_<i>x</i>Se_1–<i>x</i>) through Monotonous Alloying

Bismuth oxychalcogenides (Bi₂O₂X, where X = S, Se, Te) have garnered significant attention recently due to their high electron mobility, air stability, and excellent photoelectric properties. Therefore, precise control and optimization over the properties of these novel quasi-2D materials are crucial for practical applications. In this study, we synthesize epitaxial films of Bi₂O₂(S,Se) by the monotonous alloying of sulfur (S) and selenium (Se). Our findings reveal that the lattice constants, band gaps, and electrical properties of the films vary according to the elemental composition. Further, we observed an enhanced field-effect mobility of ∼215 cm²/(V s) and an on/off ratio of ∼10⁶ in the Bi₂O₂(S_0.4Se_0.6) heterostructures with a Bi₂SeO₅ (BSO) oxide layer. With these efforts, this work establishes a pathway toward developing novel designs for 2D Bi₂O₂X materials.