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 u sed Co investigate AlxGa1-xSb/GaSb heterostructures (0.2 <x <1) grown by mo lecular beam epitaxy. We show that the AlCs+ and GaCs+ intensities, obtaine d by using caesium cluster secondary-ion-mass spectrometry mode, vary linea rly with the relative concentrations, and therefore, allows us to evaluate quantitatively the aluminum and gallium contents in the epitaxial layers. I ntermixing of Ga/Al species at the GaSb/AlSb interfaces could be clearly de tected by secondary-ion-mass spectrometry and is also confirmed by high-res olution x-ray diffraction. The intermixing is the result of a particular me chanism in order to minimize the strain energy, and occurs prior to the lat tice relaxation, which generates structural defects taking place. The analy ses 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 contamin ation 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 str ucture (matrix effects) contrary to what occurs for single As ions. (C) 200 1 American Vacuum Society.