Stresses in bi-material GaN assemblies

Simple, easy-to-use, and physically meaningful analytical ({''}mathematical{''}) models are suggested for the assessment of the lattice- and thermal-mismatch stresses in bi-material semiconductor, and particularly GaN, assemblies. The developed models are used to evaluate and to compare these two types of stresses. It is concluded that, unless specially pre-engineered substrates are employed, even if a reasonably good lattice match takes place (as, e.g., in the case of a GaN film fabricated on a SiC substrate, when the lattice-mismatch strain is only about 3%), the lattice-mismatch stresses are still considerably higher than the thermal stresses. This is true even when the temperature change from the semiconductor growth temperature to a low (operation or testing) temperature is significant, and the thermal stresses are, therefore, the highest. The developed models can be used, before the actual experimentation and/or fabrication is carried out, to assess the merits and shortcomings of a particular GaN or another semiconductor crystal growth technology, as far as the expected stresses are concerned. (c) 2011 American Institute of Physics. {[}doi: 10.1063/1.3638702]