Modeling of residual stresses for thermally strained GaN/Al2O3 heterostructures

A finite element model and a specialized constitutive formulation were used to predict the evolving interfacial thermal mismatch stresses and strains in gallium nitride/alumina epitaxial layered systems. The constitutive formulation was based on having the coefficients of thermal expansion vary as a function of temperature for both material systems, which were assumed to be transversely isotropic. Different layer configurations were investigated, and it is shown that layer geometry is controlled by the evolution of induced thermal mismatch properties and residual stresses.