MBE REGROWTH OF GAAS ALGAAS STRUCTURES ON RIE PATTERNED SUBSTRATES/

GaAs/AlGaAs heterostructures with excellent morphology and high lumine scence yield were regrown by molecular beam epitaxy on nonplanar wafer s patterned by reactive ion etching with SiCl4 or CCl2F2. Faceted grow th occurs on pattern edges, depending on adatom species, crystallograp hic planes, growth parameters and pattern sizes. While shallow etched structures (<1OO nm) are planarized during regrowth, independent of th eir orientation, deep etched ridges or grooves (>300 nm) aligned in th e [011]-direction are isolated from the surrounding surface by distinc t trenches due to shadowing effects. Narrow ridges (<1 mu m) with widt hs smaller than the migration length of the Ga atoms exhibit very smoo th (011) facets at the sides and (111) B-facets on the top. This growt h behaviour is applied for the direct growth of isolated nanostructure s. On the other hand, the planarizing regrowth on shallow etched wafer s is used to build in a thin n-AlGaAs blocking layer in the p-AlGaAs c ontact layer of a vertical cavity surface emitting laser diode to redu ce current spreading.