4 - Strain and composition determination in semiconducting heterostructures by high-resolution X-ray diffraction

Abstract

In this chapter, the basics of the methods for measuring the strain and the composition in two- and zero-dimensional structures by means of high-resolution X-ray diffraction techniques and laboratory X-ray sources are presented, with the aim of introducing these techniques to the reader. The main physical properties for defining the strain state of a heterostructure are given and the basics of the elasticity theory for cubic and hexagonal crystals are also introduced. The X-ray diffraction method for determining the composition in semiconducting alloys is explained, allowing to conclude that the lattice parameter measurement method is one of the most accurate way to determine the composition, provided that the composition versus the lattice parameter dependence is known. The comparison between composition values obtained from X-ray diffraction method and that determined by other analytical techniques has allowed to measure a deviation from the linear Vegard law in several semiconducting alloys. The experimental determination of the deviation of the Vegard law in the InGaAs alloy is reported.