Composition and lattice-mismatch measurement of thin semiconductor layers by x-ray diffraction

X-ray diffraction methods for determining alloy composition and mismatch have been used for many years by measuring the separation of peaks in a high-resolution diffractogram. This method can still be used, but not for layer thicknesses below 1–2 μm. The diffractogram may appear simple to interpret, for example, two diffraction peaks from a single layer on a substrate, but simple measurement of peak separation can lead to significant errors in determining the mismatch and hence alloy composition. This paper gives examples of peak shifting with thin layers and shows how, by simulating the diffraction profiles, a reliable determination of mismatch, and hence alloy composition can be made.