Molecular Beam Epitaxy of Two-Dimensional GaTe Nanostructures on GaAs(001) Substrates: Implication for Near-Infrared Photodetection

Abstract

Molecular beam epitaxy of two-dimensional (2D) GaTe nanostructures on GaAs(001) substrates has been reported in this study. A trade-off between growth temperature and growth time (thickness) is a prerequisite for governing the crystal morphology of 2D GaTe materials from 2D epitaxial thin films to pseudo-one-dimensional (1D)/2D nanostructures (including nanorods, nanotriangles, and nanodendrites). Importantly, through real-time azimuthal reflection high-energy electron diffraction, a coexistence of hexagonal-GaTe (h-GaTe) and monoclinic-GaTe (m-GaTe) phases in the film was explored, corresponding to formation of lateral h/m-GaTe heterophase homojunctions. In addition, we found that utilizing a GaN/sapphire platform instead of the GaAs(001) substrate promotes formation of a single-phase h-GaTe in the thin film, which could be due to the surface-symmetry matching between the GaN/sapphire platform and the h-GaTe phase. Together with observing an asymmetric emission broad band of ∼1.76 eV that comes from the pseudo-1D m-GaTe phase, we provide convincing evidence that the emission feature located at 1.46 eV originates from the near-band-edge emission of the 2D h-GaTe epitaxial thin film. These results are meaningful in providing practical schemes to control the crystal phases of 2D GaTe materials and realize either hexagonal–monoclinic heterophase lateral homojunctions or single-phase h-GaTe epitaxial thin films on a wafer scale for future functional (opto)electronic devices, especially for near-infrared photodetectors.