Use of quantitative EELS and cathodoluminescence for study of carrier confinement and diffusion in self organized vertical quantum wells

When Al_xGa_1-xAs layers are grown on V-grooved GaAs substrates by metal organic chemical vapour deposition (MOCVD), a Ga rich vertical quantum well (VQW) appears in the V-groove centre. The width and Ga enrichment of this structure depend on the nominal Al concentration and growth temperature. From EELS linescans and spectrum images, concentration profiles and maps of VQWs are obtained, and a subsequent bandstructure calculation shows up to three confined subleveis in the VQW. Carrier confinement in segments of modulated VQWs is demonstrated. In interconnected VQW-quantum wire structures, carrier diffusion channels were assessed by cathodoluminescence. Carrier capture into the VQW and transfer into the QWR was observed.