MBE growth and characterisation of Al(x)Ga(1-x)Sblayers on GaSb substrates

AlxGa1 - xSb layers on GaSb(0 0 1) have been grown by molecular beam epitaxy (MBE) and characterised by high-resolution X-ray diffraction (HRXRD) and secondary ion mass spectrometry (SIMS) measurements. The antimonide layers inevitably contain residual As amounting to 0.5 mol%. This cannot be avoided when growing the films in a MBE apparatus previously used for GaAs growth, at least for the applied growth temperature of 470 degrees C. Segregation processes of Ga from the GaSb buffer layer and Al from the heteroepitaxial layer into the layers above are detected by SIMS. Since monomeric Sb forms metallic films on the sample surface, the exposure to a monomeric Sb flux below 370 degrees C should be avoided in order to obtain a clean surface. The composition of the 150 nm thick quaternary AlxGa1 - xAsySb1 - y layers was determined with high precision.