UV laser surface microstructuring for the selective growth of high-quality III-V semiconductor layers

III-V semiconductors, particularly gallium nitride (GaN), are key materials for modern LED technology and high-power electronics. However, GaN production based on epitaxial lateral overgrowth (ELO) requires numerous process steps, including lithographic prestructuring and wet chemical etching of growth substrates, which are highly cost- and energyintensive. In this work, a novel process based on direct laser microstructuring of the growth substrates is presented. This approach could enable the in-line production of high-quality GaN layers in isolated dies, which could significantly reduce both costs and environmental impact. Using a UV ultrashort-pulsed laser, isolation grooves (~10 µm) are written on an AlN-coated sapphire substrate to locally suppress subsequent GaN growth and thereby achieve bottom-up segmentation into individual dies. On an Si₃N₄/AlNcoated sapphire substrate, selective laser removal of the Si₃N₄ layer in arrays of parallel scan lines leaves small Si₃N₄ features (~2 µm), which promote ELO from the exposed AlN seed layer and enable the formation of high-quality GaN layers. In addition, wide Si₃N₄ tracks (~25 µm) are preserved between adjacent patterned fields, effectively inhibiting GaN growth and thus providing an isolation into individual dies. The ablation behavior of AlN and Si₃N₄/AlN layers on sapphire is systematically investigated and GaN overgrowth experiments provide insight into the layer modification and feature size required for reliable epitaxial overgrowth and effective die isolation. The results demonstrate the strong potential of the presented direct laser-based approach as a scalable and sustainable alternative to conventional lithography-based patterning processes.