Biaxial strain and lattice constants of InN (0001) films grown by plasma-assisted molecular beam epitaxy

Abstract

We present a systematic study, using high resolution x-ray diffraction, of the in-plane a and out-of-plane c lattice parameters of high quality InN films grown by molecular beam epitaxy on GaN Al2 O3 (0001) substrates. It is found that their values are dependent on the nucleation and growth conditions. Films nucleated in a two- or three-dimensional growth mode exhibit biaxial compressive or tensile strain, respectively. The linear dependence of c on a is consistent with biaxial strain being present in the films. A biaxial strain relaxation coefficient of 0.43±0.04 is deduced. The values of the lattice constants for the case of strain-free InN are estimated to be in the ranges c=5.699±0.004 Å and a=3.535±0.005 Å. © 2006 American Institute of Physics.