Secondary-ion-mass spectrometry and high-resolution x-ray diffraction analyses of GaSb-AlGaSb heterostructures grown by molecular beam epitaxy

Secondary-ion-mass spectrometry and high-resolution x-ray diffraction are used Co investigate AlxGa1-xSb/GaSb heterostructures (0.2 <x <1) grown by molecular beam epitaxy. We show that the AlCs+ and GaCs+ intensities, obtained by using caesium cluster secondary-ion-mass spectrometry mode, vary linearly with the relative concentrations, and therefore, allows us to evaluate quantitatively the aluminum and gallium contents in the epitaxial layers. Intermixing of Ga/Al species at the GaSb/AlSb interfaces could be clearly detected by secondary-ion-mass spectrometry and is also confirmed by high-resolution x-ray diffraction. The intermixing is the result of a particular mechanism in order to minimize the strain energy, and occurs prior to the lattice relaxation, which generates structural defects taking place. The analyses also give evidence of a constant arsenic contamination (similar to0.5%) both in the GaSb buffer and in the AlxGa1-xSb layers. In fact, As contamination occurs if the molecular beam epitaxy chamber has been used previously for the growth of As-compound materials. We show that the signal obtained by using the caesium cluster secondary-ion-mass spectrometry mode AsCs+ is nearly unaffected by the changes of the Al content throughout the total structure (matrix effects) contrary to what occurs for single As ions