Characterization of buried pseudomorphic InGaAs layers using high-resolution x-ray diffraction

The thickness and composition of the InGaAs layer in GaAs/AlGaAs/InGaAs/AlGaAs/GaAs high-electron-mobility transistor devices were determined to within ±5 Å and ±0.003, respectively, using high-resolution x-ray diffraction. The combined thickness of the capping AlGaAs and GaAs layers were also determined to within ±5 Å. Although the interference effects near the substrate peak in the diffraction pattern may be identical for structures with different InGaAs thicknesses, the peak from the buried InGaAs layer will be different. In other words, if the diffraction from the buried layer is measured, one can readily distinguish between structures whose interference peaks are otherwise the same. It is also shown that the use of different reflections removes the ambiguity associated with interference peaks.