Anisotropic Thermo-Elastic Modeling and Sensitivity Analysis of Edge-Defined Film-Fed Grown β-Ga2O3

The edge-defined film-fed growth (EFG) method is the dominant industrial technique for producing large-area β-Ga2O3 single-crystal substrates, but thermal stress-induced dislocation generation remains a critical barrier. This work presents a coupled thermo-mechanical finite-element framework for thermal-stress management in EFG-grown β-Ga2O3. The central methodological contribution is a 500-sample gradient-boosting surrogate sensitivity analysis (R2=0.955, mean absolute error (MAE) =11.3 MPa) that quantitatively decomposes thermal-stress variance into controllable process factors and irreducible material-property uncertainties. The physical foundation comprises two enabling elements: (i) the full 21-component monoclinic Voigt stiffness matrix with explicit crystal–model coordinate mapping, for which the orthotropic model is rigorously shown to be exact in 2D plane strain through an exact kinematic theorem showing that the 2D plane-strain results of prior orthotropic EFG analyses are unaffected by the coupling terms, while the monoclinic formulation provides the essential foundation for future 3D studies; and (ii) a dimensionless and numerical justification for omitting melt convection, which enables 100% solver convergence (500/500 Latin hypercube samples) with stress errors < 1.5 MPa. Afterheater temperature TAH is the leading controllable parameter (35.9%), nearly tied with the elastic constant C33 (35.5%), followed by the thermal-expansion component αc (15.9%). Elevating TAH from 1900 K to 1950 K reduces the peak von Mises stress by ∼29% (COMSOL Multiphysics 6.2-verified); the 2D plane-strain baseline anchors the surrogate analysis at σmax=223 MPa, while the afterheater-free 3D configuration gives σmax=187 MPa at the crystal periphery near the solid–liquid interface. The isotropic approximation underestimates peak stress by 39.6%, confirming that directional anisotropy is essential for quantitatively reliable thermal stress prediction in monoclinic oxide crystals.