CATHODOLUMINESCENCE MICROSCOPY OF INHOMOGENEITIES IN SEMICONDUCTOR HETEROSTRUCTURES

Optically effective inhomogeneities in semiconductor heterostructures with very different origin are investigated by cathodoluminescence in conjunction with scanning electron microscopy (CL). In GaAs-AlGaAs sin gle quantum wells with different length scales of the interface roughn ess (L(R)), the CL intensity distribution is determined by the spatial resolution of CL (L(av)), when L(R) is smaller than L(av). QWs grown on a substrate tilted 2 degrees towards (($) over bar 1 $($) over bar$ $ 11)As contain a long-range roughness (mu m scale), which correlates with the surface topo,graphy. In highly strained QWs, the influence of misfit dislocations (MD) on the spatial and spectral luminescence dis tribution is investigated. MDs cause regular variations of the exciton confinement energy in the QW and hence lead to complementary CL image s recorded at two defined detection energies. In a vertically biased G aAs-AlAs superlattice, depth resolved CL measurements from the top and spectrally resolved CL imaging from the cleaved edge are performed to directly observe the spatial distribution of electric-field domains.