X-ray diffraction study of intentionally disordered (GaIn)As/Ga(PAs) heterostructures

Abstract

The influence of layer thickness fluctuations and deviation from perfect periodicity on high resolution x-ray diffraction (HR XRD) profiles are investigated experimentally and theoretically for (GaIn)As/Ga(PAs) symmetrically strained multiple quantum well heterostructures. Structural properties are deduced from the experimental HR XRD profiles by comparison with full dynamical XRD simulations. Samples with periodic thickness modulations are systematically studied with respect to periodicity, amplitude of modulation and layer mismatch. The high sensitivity of XRD in the strained (GaIn)As/Ga(PAs) material system allows a quantitative description of the nature (type), amplitude, and period of modulation. The results are experimentally compared to the lattice matched AlAs/GaAs material system. The influence of the modulation function of periodic modulations is studied. We investigate two types of graded structures with layer thickness grading either for one ternary layer (one side grading) or for both ternary layers (double side grading). The effects of grading steepness and layer mismatch are systematically studied. We develop a kinematical model which qualitatively describes specific peak characteristics of XRD patterns of one and double side graded heterostructures and allows the deduction of analytical expressions for specific peak features thus improving the understanding of measured and calculated patterns.