CHARACTERIZATION OF BURIED PSEUDOMORPHIC INGAAS LAYERS USING HIGH-RESOLUTION X-RAY-DIFFRACTION

The thickness and composition of the InGaAs layer in GaAs/AlGaAs/InGaA s/AlGaAs/GaAs high-electron-mobility transistor devices were determine d to within +/-5 Angstrom and +/-0.003, respectively, using high-resol ution x-ray diffraction. The combined thickness of the capping AlGaAs and GaAs layers were also determined to within +/-5 Angstrom. Although the interference effects near the substrate peak in the diffraction p attern may be identical for structures with different InGaAs thickness es, 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 ot herwise the same. It is also shown that the use of different reflectio ns removes the ambiguity associated with interference peaks.