Spatially resolved Raman piezospectroscopy for nondestructive evaluation of residual stress in β-Ga₂O₃ films

Abstract

In this paper, the piezospectroscopic effect for β-Ga2O3, i.e. the spectral band shift in response to strain/stress, has been calibrated from the indentation method by using spatially resolved Raman spectroscopy for quantitative stress evaluation of Ga2O3 devices, taking advantage of the crack-tip tensile stress field and the spatial probe deconvolution. A series of Vickers indentation prints were introduced on (010) and (-201) Ga2O3 single crystals, and the relationships between observed band shifts and residual stresses were clarified to determine the phonon deformation potentials of the Raman bands. Accordingly, a quantitative analysis of the residual stress field in a Ga2O3 thin film grown on (0001) sapphire by plasma assisted pulsed laser deposition was shown as an example, which revealed the presence of a gradient of incompletely released stress in the depth direction of the film.