Ni-Catalyzed GaP Nanowires and Nanosheets with Crystallographic Phase Control—Implications for Single-Material Heterostructures

III-V semiconductor nanostructures have been considered for several applications, ranging from quantum computing to optoelectronics and energy conversion [1-3]. In particular, wurtzite Gallium Phosphide nanowires work as a substrate to direct band gap hexagonal Si and SiGe alloys [4]. However, the ability to change morphologies, from nanowires to nanosheets, provides a tool to better adapt the nanostructures to the intended applications. Two-dimensional GaP materials, which have not been explored so far, would make easier their integration into device fabrication processes, and controlling crystallographic phase transition from zincblend to wurtzite provides the opportunity of creating heterostructures in a single material. Here, we explore these possibilities and report the growth of GaP nanostructures by Chemical Beam Epitaxy, catalyzed by Ni nanoparticles formed from thermal deposition of a thin Ni layer. Samples were obtained under different growth conditions, with temperatures in the range 530-590C and TEG and thermally-cracked PH3 as group III and V precursors, respectively. Electron microscopy analysis of the samples shows both nanowires and nanosheets, with the nanosheet population increasing with temperature. High resolution transmission electron microscopy reveals that nanosheets are primarily zincblend, while nanowires present a mixture of zincblend and wurtzite phases. The observed growth rates indicate that Ni serves as a better catalyst for Ga-based nanowires than Au. Atomic force microscopy of the nanosheets reveals width and length values up to 2 and 10 micra, respectively, with 50 to 100 nm thickness. Photoluminescence at low temperatures of the as-grown samples shows characteristic signal from wurtzite GaP crystal structure, with typical defect luminescence as well as optical emissions in the green spectral range at 2.16 eV and 2.20 eV with linewidths ~ 30 meV. These results indicate the feasibility of our approach to grow different types of GaP semiconductor nanostructures using Ni cataysts, and provide new possibilities of heterostructures for this single optoelectronic material. Acknowledgements: FAPESP, CNPq, CAPES<br/>References:<br/>[1] De La Mata M et. al. Nano Lett. 16, 825–33, 2016.<br/>[2] Kelrich A. et. al. Nano Lett. 16, 2837–33, 2016.<br/>[3] Sung, M. et al. Adv. Ener. Mat. 6, 1600087, 2016<br/>[4] Hauge H. I. T. et. al. Nano Lett. 15, 5855–60, 2015.