Analysis of high-resolution x-ray diffraction in semiconductor strained layers

The composition and strain of pseudomorphic epitaxial layers is measured by high-resolution x-ray diffraction. Rocking curves or reciprocal space maps are measured from several reflections from sets of lattice planes, and their peak positions combined to yield the physical parameters of interest. We show here that the peak positions are best evaluated as the centres of gravity of the peaks. These data are then analyzed using least-squares multiple linear regression. This gives best estimates of the values and the errors of the physical parameters. The analysis also provides guidance as to the best sets of reflections to measure. Asymmetric reflections are preferable to symmetric reflections; but if symmetric reflections are used then the asymmetric reflections with high angle of incidence are more valuable than with low angle of incidence. (C) 1999 American Institute of Physics. [S0021-8979(99)04014-1].