| Ultra-low energy secondary ion mass spectrometry (SIMS) depth profile analysis was performed on metal organic vapour phase epitaxy (MOVPE) grown structures. The layered systems are multi quantum well (MQW) structures composed of InAlGaAs, AlGaAs and GaAs. The structures typically consisted of GaAs substrate, 150 ÷ 500 nm GaAs buffer, MQW region and 50 ÷ 70 nm GaAs cap layer. The MQW is a 3-layer period superlattice made of 4.5 ÷ 9 nm thick InxAlyGa1-x-yAs layers and 30 nm thick GaAs or AlzGa1-zAs layers. SIMS analyses performed with the use of 880 eV Ar+ ion beam give depth profile resolution (16%-84%) of ∼3 nm measured at GaAs/InAlGaAs interface of MQW structure. Comparison of SIMS data with high resolution X-ray diffraction (HRXRD) allows to measure thickness of particular layers in the studied structures as well as indium molar fraction in quaternary compound InAlGaAs. |
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