Towards Phase-Pure Cubic GaN on GaP: Suppression of Hexagonal Inclusions by Low-Temperature Buffer Engineering

Phase-pure cubic GaN (c-GaN) was grown on GaP(001) substrates by low-pressure metal−organic chemical vapor deposition (LP-MOCVD) to evaluate the influence of substrate nitridation and low-temperature GaN buffer layers on phase stability and crystalline quality. Structural and morphological characterization by X-ray diffraction (XRD), Raman spectroscopy, and atomic force microscopy (AFM) showed that the incorporation of a low-temperature buffer layer effectively suppresses hexagonal GaN inclusions and promotes single-phase cubic growth. Raman spectra exhibited the characteristic vibra-tional modes of c-GaN, while XRD analysis revealed narrower c-GaN(200) diffraction peaks, indicating improved crystallinity, larger crystallite size, and reduced defect-related broadening. AFM measurements further demonstrated enhanced grain coalescence and surface uniformity. These findings highlight low-temperature buffer-layer engineering as an effective strategy for stabilizing cubic GaN and improving the structural quality of c-GaN/GaP heterostructures for future electronic and optoelectronic applications.