X-ray interference measurement of ultrathin semiconductor layers

We have characterized, using the interference structure in x-ray rocking curves, a single or double strained GaInP layer grown on an InP substrate. The measured GaInP layer thicknesses are 9±3 Å and 107±3 Å for the single strained layer samples and 7 Å/50 Å and 32 Å/32 Å for the double strained layer samples. The rocking curve results for the 107 Å single-barrier sample and the 7 Å/50 Å double-barrier sample agreed well with the cross-section transmission electron microscopy data and the secondary-ion mass spectrometry data. The x-ray interference structure for the single strained barrier samples indicates the existence of many half-monolayer steps within the 1×1 mm² x-ray beam spot at each GaInP/InP interface.