MBE REGROWTH OF GAAS/ALGAAS STRUCTURES ON RIE PATTERNED SUBSTRATES

GaAs/AlGaAs heterostructures with excellent morphology and high luminescence yield were regrown by molecular beam epitaxy on nonplanar wafers patterned by reactive ion etching with SiCl4 or CCl2F2. Faceted growth occurs on pattern edges, depending on adatom species, crystallographic planes, growth parameters and pattern sizes. While shallow etched structures (<1OO nm) are planarized during regrowth, independent of their orientation, deep etched ridges or grooves (>300 nm) aligned in the [011]-direction are isolated from the surrounding surface by distinct trenches due to shadowing effects. Narrow ridges (<1 mu m) with widths smaller than the migration length of the Ga atoms exhibit very smooth (011) facets at the sides and (111) B-facets on the top. This growth behaviour is applied for the direct growth of isolated nanostructures. On the other hand, the planarizing regrowth on shallow etched wafers is used to build in a thin n-AlGaAs blocking layer in the p-AlGaAs contact layer of a vertical cavity surface emitting laser diode to reduce current spreading.