Analysis of biaxial strain in InN(0001) epilayers grown by molecular beam epitaxy

The in-plane lattice parameters of InN, GaN and Al2O3 in a InN/GaN/Al2O3(0001) heterostructure have been measured as a function of temperature in the range of 25-350 degrees C, using high resolution X-ray diffraction. The results reveal that both the GaN and InN crystals follow the in-plane thermal expansion of the Al2O3 substrate's lattice and there is no rearrangement of misfit dislocations at the InN/GaN and GaN/Al2O3 interfaces. It was also found that either compressive or tensile character of residual biaxial strain is possible for the InN films, depending on the two-dimensional (2D) or three-dimensional (3D) growth mode of InN on the GaN(0001) buffer layer. The tensile strain is inherent to the nucleation and coalescence of 3D islands. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.