Three-dimensional characterization of laser-induced stress in a bulk GaN substrate using stimulated Raman scattering microscopy

The three-dimensional (3D) stress distribution in a bulk GaN substrate with laser-induced indentations for laser slicing was characterized using stimulated Raman scattering (SRS) microscopy. Local shifts in the Raman peak corresponding to the E2H mode were detected around the indentations, indicating the induction of local stress. The spatial distribution of internal stress was successfully visualized, revealing a clear in-plane anisotropy with compressive and tensile stresses along the a- and m-axes, respectively, as well as its extension in the depth direction. SRS microscopy enables the 3D visualization of residual stress in bulk GaN substrates, facilitating the optimization of fabrication processes.