Characterization of (Al,Ga)As/GaAs Multilayer Structures by X-Ray Interference

Abstract

ABSTRACTAn experimental study of x-ray interference effects from GaAs/AlxGa1−xAs multilayer structures was conducted. The presence of a GaAs layer, whose thickness ranged from 50 Å to 10 μm, between two Al0.30Ga0.70As layers was found to significantly affect the x-ray rocking curves from these structures. We determined both the thickness and the composition of the AlxGa1−xAs layers and the thickness of the GaAs layers by comparing the rocking curves to simulated ones using a dynamical x-ray diffraction model. A sensitivity analysis showed that the thickness predicted for the GaAs buried layer was precise to within 90 Å for a ≃ 2000 Å GaAs layer and that the barrier layer Al content and thickness could be determined to within 1% and 80 Å, respectively for ≃ 5000Å layers. This analysis also showed that, within experimental resolution limits, the structure determined from comparing simulated and experimental rocking curves was unique. Both the limits of this technique in determining interfacial grading and applications to specific device structures and other materials systems are discussed.