Janus structures of the polymorph of gallium monochalcogenides: first-principles examination of GaXY (X/Y = S, Se, Te) monolayers.

Group III monochalcogenide compounds can exist in different polymorphs, including the conventional and phases. Since the bulk form of the -group III monochalcogenides has been successfully synthesized [ (2006) 235202], prospects for research on their corresponding monolayers have also been opened. In this study, we design and systematically consider a series of Janus structures formed from the two-dimensional phase of gallium monochalcogenide GaXY (X/Y = S, Se, Te) using first-principles simulations. It is demonstrated that the Janus GaXY monolayers are structurally stable and energetically favorable. GaXY monolayers exhibit high anisotropic mechanical features due to their anisotropic lattice structure. All Janus GaXY are indirect semiconductors with energy gap values in the range from 1.93 to 2.67 eV. Due to the asymmetrical structure, we can observe distinct vacuum level differences between the two surfaces of the examined Janus structures. GaXY monolayers have high electron mobility and their carrier mobilities are also highly directionally anisotropic. It is worth noting that the GaSSe monolayer possesses superior electron mobility, up to 3.22 × 10 cm V s, making it an excellent candidate for potential applications in nanoelectronics and nanooptoelectronics.