PA-MBE growth of GaN nanowires on graphene-coated glass for heterogeneous optoelectronic integration

The growth mechanism and optoelectronic performance of GaN nanowires on amorphous fused silica glass with and without a graphene interlayer were investigated using plasma-assisted molecular beam epitaxy. Nanowires grown on bare glass exhibited dense and uniform nucleation, whereas those grown on graphene showed a void-rich morphology with mixed polarity and pronounced stacking faults. Despite this morphological non-uniformity, X-ray diffraction pole figures and transmission electron microscopy revealed that the graphene interlayer partially promoted out-of-plane ordering through a quasi–van der Waals epitaxial mechanism. Raman spectroscopy and photoluminescence measurements further showed that graphene-assisted nanowires exhibit strong stacking-fault-related emissions, while nanowires on bare glass are dominated by deep-level yellow luminescence. Lateral photodetectors fabricated through planarization and Ti/Au metallization demonstrated significantly enhanced photocurrent and responsivity for graphene-assisted nanowires under 375 nm illumination. These results elucidate how two-dimensional interlayers modulate polarity, defect formation, and device performance in GaN nanowires grown on amorphous substrates, providing insight into scalable GaN-based optoelectronics on glass.