ABSTRACT
This chapter investigates the reproducibility of the measurements and the effect of some of the growth parameters. Accurate determination of the Al content of AlGaAs/GaAs epitaxial layers is of great practical interest. Usually the Al content of epitaxial layers is calculated from a measurement of the difference in lattice parameters between the epitaxial AlGaAs layer and the GaAs substrate. Measured lattice parameter differences are converted into compositions by using the Poisson’s ratio and end-member lattice parameters. However, these numbers are not well known which makes the determination of Al concentration problematic. An alternative approach has been to use epitaxial layers of the end-member AlAs as a calibration standard; there has recently been renewed interest in this method. Another approach to Al calibration was to grow a layer of AlAs as part of the structure so that it could be used as a true internal standard.
