Lateral variations of the quantum well confinement energy reflected by SEM-cathodoluminescence

The potential of cathodoluminescence (CL) in connection with scanning electron microscopy (SEM) for the investigation of the lateral variation of interfaces in this film heterostructures is examined. GaAs/AlxGa1−xAs single and multiple quantum wells were prepared by molecular beam epitaxy under different conditions resulting in various surface morphologies. Spectrally resolved CL line profiles, which provide information on lateral variations of the exciton confinement energy (E) are compared with the surface structure imaged by SEM or atomic force microscopy. For surface undulations with periods larger than the spatial resolution (L) of CL, a direct correlation between surface and interface features was proven. In the case of a statistical distribution of small interface growth islands, the period of the CL intensity modulation is determined by L. However, the modulation depth of the CL intensity contains information on the underlaying disorder. For substrates, in which misfit dislocations were generated during the MBE growth of the heterostructure, we found variations of E along two sets of straight lines perpendicular to each other.