Analysis of semiconductor heterostructures using high resolution X-ray diffraction techniques

The characteristics of semiconductor heterostructures are studied through high resolution X-ray diffraction techniques, rocking curve and reciprocal space mapping techniques.; System configuration of an X-ray diffractometer and its optical elements' basic properties and detailed performance procedures of the optical elements are discussed.; The effect of goniometer mounting conditions on the characteristics of reciprocal space maps and rocking curves geometry was studied. The coherent Bragg diffraction portion of the reciprocal space maps showed a strong dependence on chi and ϕ angles of the sample goniometer. The orientation of intensity contours in the reciprocal space map rotated by chi and ϕ setting, respectively. This rotation is shown to be due to the changing breadth of diffraction profile of the sample crystal. By changing the vertical beam width for the scattered beams, it was found that a larger vertical beam width causes a faster rotation in the reciprocal space map contour. The rocking curve FWHM and peak position were also dependent on the chi and ϕ angle setting. The mechanism of the rotation and according simulation was studied.; The structural properties of metamorphic InxAl1-x As buffer layers grown on GaAs substrate were studied using the reciprocal space mapping technique. Three types of metamorphic samples were examined, including step-graded, single-slope linearly graded, and dual-slope linearly graded buffer layer samples. The residual strain, crystallographic tilt, and degree of relaxation of the epilayer were deduced from the reciprocal space maps. The related properties of mosaic spread and degree of relaxation are discussed. The effect of the inverse-step top layer for improvement of relaxation is shown to be less than expected due to the insufficient step back of composition of the top layer.; The measurement technique of the absolute lattice parameter independent of the external conditions such as the sample mounting condition was studied. An improved procedure for measuring lattice parameter was developed based on the zone axis scheme. Measured data was processed with nonlinear least-squares curve fitting algorithm. The measured lattice parameter showed an accuracy of 10-5 A of error range.