Alloying-Induced Crystal-Phase Transition in InxGaySez Alloys Grown on C-Sapphire Substrates by Molecular Beam Epitaxy: Implication for Next-Generation Optoelectronics

High Resolution Image Download MS PowerPoint Slide Going beyond graphene and transition-metal dichalcogenides, group III–VI metal chalcogenides (GIIIMCs) with diverse crystallinities appear as new rising stars and have recently attracted numerous interesting physics for prospective optoelectronics, even though they face crucial challenges in their epitaxial technology. In this work, for the first time, large-compositional range In x Ga y Se z ternary alloys have been deposited on c-sapphire substrates by molecular beam epitaxy (MBE). We explored that MBE of In x Ga y Se z on c-sapphire substrates undergoes a two-dimensional (2D)-to-three-dimensional (3D) structural phase transition, resulting in mixed-dimensional alloy heterostructures of 2D hexagonal-In x Ga y Se z and 3D zinc-blende/wurtzite In x Ga y Se z . The 2D-to-3D transition supposedly originates from the indium segregation and depends strongly on the indium composition. We also found that modulating the growth parameters such as In/Ga ratio, deposition temperature, and deposition time could be an effective way to precisely control the 2D/3D crystal phases of the alloys. Overall, the results pave the way for phase/physical engineering of GIIIMC-based alloys through MBE and realizing mixed-dimensional alloy heterostructures for multifunctional applications.