Cracking of III-nitride layers with strain gradients

Experimental results are demonstrated for the cracking of nominally compressed AlyGa1-yN layers grown on AlxGa1-xN buffer layers with smaller lattice constants (y < x). The authors present a theoretical analysis showing that the inclination of pure edge threading dislocation lines effectively reduces the compressive stress, causing relaxation, and after reaching a certain thickness begins to generate the tensile stress gradient responsible for cracking. The critical layer thickness for crack nucleation in such a gradient elastic field has been found. The results of the modeling are in good agreement with experimental observations of crack onset in nominally compressed nitride layers. (c) 2006 American Institute of Physics.