ABSTRACT
Cracks form in the tensile epilayer of AlGaN deposited on GaN buffers above a critical thickness. If the layer is restricted to a thickness less than 3 × 1012 f−2m (f is the lattice mismatch) cracks will not occur. Increasing thickness leads to a population of cracks on each of the equivalent {11̅00} habit planes. They display various profiles depending upon the time of formation of the crack. Because of stress relief in the vicinity of an existing crack no examples of crack crossover have been observed.
