Self-Catalyzed Vapor-Liquid-Solid Growth of GaS Nanobelt

Among group-III chalcogenides, which are atomic-layered semiconductors, GaS shows a large layer-number-dependent bandgap energy from 2.5 eV (bulk) to 3.4 eV (monolayer) corresponding to blue and ultraviolet light wavelengths, respectively [1]. This unique property makes it a promising material for photonic devices and water-splitting photocatalysts [2, 3] and also an important component for group-III chalcogenide heterostructures. Furthermore, 1D structures of 2D layered materials, nanobelt or nanoribbon, would enable novel quantum devices and nanodevice integration. In this work, we demonstrate the synthesis of GaS nanobelt by means of self-catalyzed vapor-liquid-solid (VLS) growth.<br/>GaS was grown on a sapphire wafer by metalorganic chemical vapor deposition (MOCVD). Triethylgallium (TEGa) and diethylsulfide (DES) were used as Ga and S sources, respectively. VLS growth of 1D GaS-nanobelts occurs from Ga clusters, which can be formed under a Ga-rich surface growth condition obtained at high [TEGa]/[DES] supply ratios, while 2D GaS layers are grown at low [TEGa]/[DES] supply ratios. Thus, the dimension of the GaS structure can be controlled by MOCVD growth conditions.<br/>To evaluate the optical quality of the GaS nanobelt, we fabricated a photodetector (width: 900 nm, thickness: 100 nm, channel length: 2 μm). A photocurrent was generated under light irradiation with photon energies larger than 2.5 eV (wavelengths shorter than 500 nm), corresponding to the bandgap energy of GaS. The dark current was lower than the detection limit of our measurement system. A high ON/OFF ratio (&gt; 1000) at a wavelength of 400 nm was obtained at the applied voltage of 10 V. This good photoresponsivity indicates that the VLS-grown GaS nanobelt has a high enough quality for device operation. The development of high-quality 1D GaS nanobelt synthesis on a wafer opens up opportunities for group-III chalcogenide nanodevice applications as well as the exploration of novel quantum phenomena.<br/><br/>References:<br/>[1] C. S. Jung <i>et al</i>., ACS Nano <b>9</b>, 9585 (2015).<br/>[2] Y. Lu <i>et al</i>., Adv. Mater. <b>32</b>, 1906958 (2019).<br/>[3] H. L. Zhuang <i>et al</i>., Chem. Mater. <b>25</b>, 3232 (2013).