Enabling Type I Lattice-Matched Heterostructures in SiGeSn Alloys Through Engineering Composition and Short-Range Order: A First-Principles Perspective

Tuning the composition in group IV alloys can significantly change their electronic structures, enabling a broad range of properties for electronic, photonic, and topological applications. As the growth and device design of group IV alloys often require heterostructures, achieving lattice match is crucial for fabricating high-quality heterojunctions. Here, by combining
ab initio
calculations and Monte Carlo sampling, we investigate the structures and band offsets of two distinct types of lattice-matched junctions: a traditional SiGeSn/Ge heterojunction, which requires an optimal Si-to-Sn ratio to match the lattice constant of Ge, and a short-range-order (SRO) induced SiGeSn/SiGeSn homo-composition heterojunction composed of two chemically and compositionally identical ternary Si-Ge-Sn alloys but with distinct degrees of SRO. For SiGeSn/Ge heterojunction, our analysis shows significant differences exist in the predicted band offsets between the full first-principles calculations and the commonly adopted empirical models, thus suggesting a high uncertainty for SiGeSn/Ge to function as the proposed type I heterojunction. In contrast, the SRO-induced homo-composition heterojunctions are demonstrated to carry a clear type I band alignment with desirable band offsets that can be tailored through engineering the degree of SRO. The inherent lattice match and chemical homogeneity of the SRO-induced homo-composition heterojunctions offer great advantages and potential for advanced optical applications.