The influence of nitridation temperature on 2D-MoS₂-assisted gallium nitride growth using molecular beam epitaxy

The epitaxial growth of high-quality gallium nitride (GaN) films on two-dimensional (2D) molybdenum disulfide (MoS₂) substrates is a critical challenge in advancing semiconductor technology for innovative electronics and optoelectronics. This study investigates the effect of pre-nitridation temperature (750 °C and 600 °C) on the structural and optical properties of GaN films grown via molecular beam epitaxy (MBE) on chemical-vapor-deposited MoS₂/c-sapphire substrates. Characterization techniques, including RHEED, FE-SEM, AFM, Raman spectroscopy, XPS, HR-XRD, PL spectroscopy, and TEM, were used to evaluate MoS₂ layer and GaN films. Results indicate that the temperature of pre-nitridation on 2D MoS₂ buffer layer significantly affects the quality of GaN films. At 750 °C, the partially degraded MoS₂ layer led to rougher surfaces for the epitaxial growth of GaN, which had broader FWHM in HR-XRD, and increased defect-related emissions in PL spectra. Conversely, at 600 °C, the MoS₂ layer remained intact, resulting in smoother surfaces, improved crystallinity, and fewer defect states for the GaN film. TEM analysis confirmed successful van der Waals epitaxy at the lower temperature, while degradation of the MoS₂ layer was evident at higher temperatures. This study provides valuable insights into optimizing pre-nitridation conditions to achieve superior GaN films on 2D MoS₂ substrates, paving the way for enhanced GaN-based electronic and optoelectronic devices.