OPTIMAL EPILAYER THICKNESS FOR INXGA1-XAS AND INYAL1-YAS COMPOSITION MEASUREMENT BY HIGH-RESOLUTION X-RAY-DIFFRACTION

The composition of InxGa1-xAs and InyAl1-yAs epitaxial layers on InP s ubstrates can be measured by high-resolution x-ray diffraction (HRXRD) in many cases. If layers are too thick, however, substantial lattice relaxation will occur, requiring multiple asymmetric scans to determin e composition. If layers are too thin, they will not produce a distinc t Bragg peak. Based upon measurements of both coherent and relaxed lay ers as well as simulations, we have determined the range of epilayer t hickness over which a single HRXRD scan yields the composition of InxG a1-xAs and InyAl1-yAs layers to within 1%. Calibration layers grown wi thin this range allow fast and accurate characterization.