Investigation of the compositional depth profile in epitaxial submicrometer layers of A^IIIB^V heterostructures

The compositional depth profile in semiconductor heterostructures can be determined from X-ray diffraction patterns. Different grading profiles were studied through theoretical simulations with regard to their features in the rocking curve. It was found that the thickness and the grading of a particular layer cannot be determined independently of each other. A linear grading gives rise to an increased peak width of the layer diffraction peak whereas an exponential grading can be detected from the damping of high-order interference fringes. The exponential model can be applied to determine the abruptness of the heterointerfaces. The proposed evaluation method of experimental rocking curves includes the case of overlapping peaks of the layer and the substrate diffraction. The simulation results are discussed for a GaAs/Ga_1-xAl_xAs/GaAs[001] double heterostructure. When the experimental resolution is taken into account, the sensitivity of the interface width determination was 100-200 Å.