In-situ Raman tomography of wide-bandgap homoepitaxial interfaces: A case study on 4H-SiC at elevated temperatures

In this report, we introduce a non-invasive Raman method that enables tomographic imaging of buried interfaces in wide-bandgap epitaxial structures. Using visible-wavelength excitation ( λ = 532 nm ), the approach achieves penetrative depth sensitivity without sample cleaving. The protocol utilizes depth scans ± 10 μ m relative to the epilayer surface to monitor the intensity of distinct epilayer and substrate phonon-plasmon-coupled modes. The difference between the mode intensity curves defines the nominal distance of the objective ( d ). Combined with ellipsometric data for the epilayer refractive index ( n 2 ), the vertical scan yields the epilayer thickness (optical distance) of d n 2 . Horizontal maps, enhanced by signal deconvolution, enable three-dimensional projections of the material composition. With an enclosed heating stage, the procedure can be extended from room temperature to 873 K, providing projections of buried layers under validation-relevant temperatures. Beyond the methodological demonstration, the proposed Raman tomography approach offers a practical route for non-destructive inspection of buried interfaces in wide-bandgap semiconductor structures. The capability to visualize subsurface layer morphology and interface integrity at temperatures up to 873 K makes the method attractive for process monitoring, reliability assessment, and failure analysis of SiC, GaN, Ga 2 O 3 , and diamond devices intended for high-power, high-temperature, radiation-hard, and harsh-environment applications.