Cross-sectional scanning tunneling microscopy of InAsSb/InAsP superlattices

Cross-sectional scanning tunneling microscopy ~STM! has been used to characterize compositional structures in InAs0.87Sb0.13 /InAs0.73P0.27 and InAs0.83Sb0.17 /InAs0.60P0.40 strained-layer superlattice structures grown by metal-organic chemical vapor deposition. High-resolution STM images of the ~110! cross section reveal compositional features within both the InAsxSb12x and InAsyP12y alloy layers oriented along the @1̄12# and @11̄2# directions—the same as those in which features would be observed for CuPt–B type ordered alloys. Typically one variant dominates in a given area, although occasionally the coexistence of both variants is observed. Furthermore, such features in the alloy layers appear to be correlated across heterojunction interfaces in a manner that provides support for III–V alloy ordering models which suggest that compositional order can arise from strain-induced order near the surface of an epitaxially growing crystal. Finally, atomically resolved ~11̄0! images obtained from the InAs0.87Sb0.13 /InAs0.73P0.27 sample reveal compositional features in the @112# and @1̄1̄2# directions, i.e., those in which features would be observed for CuPt–A type ordering. © 1999 American Vacuum Society. @S0734-211X~99!08404-8#