Nanometer-scale compositional variations in III-V semiconductor heterostructures characterized by scanning tunneling microscopy

Nanometer-scale compositional structure in InAsxP12x/InNyAsxP12x2y //InP heterostructures grown by gas-source molecular beam epitaxy and in InAs12xPx/InAs12ySby/InAs heterostructures grown by metalorganic chemical vapor deposition has been characterized using cross-sectional scanning tunneling microscopy. InAsxP12x alloy layers are found to contain As-rich and P-rich clusters with boundaries formed preferentially within ~1̄11! and ~11̄1! crystal planes. Similar compositional clustering is observed within InNyAsxP12x2y alloy layers. Imaging of InAs12xPx/InAs12ySby superlattices reveals nanometer-scale clustering within both the InAs12xPx and InAs12ySby alloy layers, with preferential alignment of compositional features in the @1̄12# direction. Instances are observed of compositional features correlated across a heterojunction interface, with regions whose composition corresponds to a smaller unstrained lattice constant relative to the surrounding alloy material appearing to propagate across the interface. © 1999 American Vacuum Society. @S0734-2101~99!15204-7#