STEM/EDX microanalysis of compositional fluctuations in semiconductor multi-quantum-well structures
Specimens of a GaAs/GaAlAs multiple-quantum-well structure grown by MOCVD have been examined in a scanning transmission electron microscope (STEM) fitted with a field emission gun. Energy dispersive X-ray analysis has been used to identify chemical non-uniformities of about 1 nm in width, which can be seen in STEM imaging. Although accurate quantification is difficult, analysis has shown these features to be regions of increased Al concentration. These findings are consistent with results obtained by high-resolution electron microscopy with multi-slice image simulation.