Perturbation method of analysis of crystal truncation rod data

A new method of direct inversion of crystal truncation rod (CTR) data is demonstrated for the analysis of layered semiconductor heterostructure materials. This method is based on approximations that are valid when the electron density deviations and lattice strain are small in the regions of the sample close to a well defined surface. The CTR diffraction pattern can then be regarded as a perturbation with respect to that of an ideal surface. The direct inversion method is shown to work for the analysis of a series of InP/GaInAs/InP heterostructures. The ability to recover strain information is demonstrated with a model calculation. The beginning of breakdown of the perturbation approximation is seen and explained in both cases.