Controlled Synthesis of Ultrathin Hexagonal-GaTe on MoS 2 Via Strain Engineering

Ultrathin GaTe, with direct bandgap and relatively high charge density, holds great potential in the field of optoelectronic devices. As compared with monoclinic-phase GaTe (m-GaTe), hexagonal-GaTe (h-GaTe) has the potential to be achieved with ultrathin thickness, but the thermodynamical stability further limits it further fabrications as well as the applications. In this work, by introducing two-dimensional MoS2 as the substrate, we successfully realized the phase-controlled synthesis of ultrathin h-GaTe rather than m-GaTe, leading to high quality h-GaTe/MoS2 heterostructures. Theoretical calculation studies reveal that GaTe with hexagonal phase is more thermodynamically stable on MoS2 template, which can be attributed to the strain stretching and the formation-energy reduction. Based on the achieved p-n heterostructures, optoelectronic devices are designed and probed, where remarkable photoresponsivity (32.5 A/W) and fast photoresponse speed (< 50 μs) are obtained under zero bias voltage, indicating well-behaved photo-sensing behaviors. The study here could offer a good reference for the controlled growth of the relevant materials, and the achieved GaTe/MoS2 heterostructure will find promising applications in future integrated electronic and optoelectronic devices and systems.