Molecular Beam Epitaxy\nof Mixed Dimensional InGaSe/GaSe\nHybrid Heterostructures on C‑Sapphire

Molecular beam epitaxy (MBE) of InGaSe/2D-GaSe/sapphire\nhybrid\nstructures has been reported in this study. We explore that MBE of\nthe InGaSe layer on 2D-GaSe/sapphire results in a mixed dimensional\nalloy, comprising two-dimensional (2D) hexagonal-In<sub><i>x</i></sub>Ga<sub>1–<i>x</i></sub>Se and three-dimensional\n(3D) zinc blende (InGa)<sub>2</sub>Se<sub>3</sub>, in which the 3D\none is more favorable. It is also revealed that the surface morphology\nof the underneath 2D-GaSe layer grown under different modes, i.e.,\nscrew-dislocation-driven (SDD-GaSe) and layer-by-layer (LBL-GaSe),\nsignificantly governs the epitaxial behavior of the InGaSe top layer.\nIndeed, in the case of the InGaSe alloy grown on 2D LBL-GaSe, it is\nmore and more preferable to nucleate from the edges of GaSe triangular\nflakes with increasing deposition temperature, thus promoting lateral\ngrowth. On the other hand, the surface morphology of InGaSe alloy\non 2D SDD-GaSe appears to have a high density of nanoclusters. Moreover,\na structural transition from 2D-to-3D has been recognized from in-situ\nRHEED observation, in which its on-set point is likely accelerated\nat lower growth temperatures. The gain from this study benefits our\nunderstanding of the mixed dimensional GaSe-based heterostructures\nby MBE, in terms of exploring semiconductor physics and widening potential\napplications of group-III metal chalcogenides.