Cross-sectional scanning tunneling microscopy of InAsSb/InAsP superlattices

Cross-sectional scanning tunneling microscopy (STM) has been used to charac terize compositional structures in InAs0.87Sb0.13/InAs0.73P0.27 and InAs0.8 3Sb0.17/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 InAsxSb1-x and InAsyP1-y alloy layers oriented along the [(1) over bar 12] and [<1(1)over bar>2] directions-the same as those in which features would be observed fo r CuPt-B type ordered alloys, Typically one variant dominates in a given ar ea, although occasionally the coexistence of both variants is observed. Fur thermore, such features in the alloy layers appear to be correlated across heterojunction interfaces in a manner that provides support for m-V alloy o rdering models which suggest that compositional order can arise from strain -induced order near the surface of an epitaxially growing crystal. Finally, atomically resolved (110) images obtained from the InAs0.87Sb0.13/InAs0.73 P0.27 Sample reveal compositional features in the [112] and [<(11)over bar> 2] directions, i.e,, those in which features would be observed for CuPt-A t ype ordering. (C) 1999 American Vacuum Society. [S0734-211X(99)08404-8].