XPS study of the InxGa1-xAs/GaAs superlattice

Strained InxGa1-xAs/GaAs superlattices have been grown on GaAs(100) substrates using a metal-organic chemical vapour deposition (MOCVD) apparatus. Fabricated heterostructures have been investigated by the selected area XPS depth profiling technique. The measurements have been carried out using optimized Ar+ ion sputtering conditions. The width of the heterointerfaces has been studied after correction of the experimental profiles (In3d5/2, Ga2p3/2 and Auger Ga LMM, In MNN peaks) for the influence of electron escape depth. The linear dependence of depth resolution DELTA(z) on the sputtering depth, caused by sputtering induced surface roughening, is determined from experimental profiles. The initial depth resolution DELTA(z) almost-equal-to 3 nm is degraded to DELTA(z) almost-equal-to 8 nm at depth z almost-equal-to 100 nm. Quantitative depth profiles of the investigated heterointerfaces are derived using calibrated elemental sensitivity factors and ion sputtering rates. The results are found to be in good agreement with X-ray diffractometry and transmission electron microscopy data.