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

Nanometer-scale compositional structure in InAsxP1−x/InNyAsxP1−x−y//InP heterostructures grown by gas-source molecular beam epitaxy and in InAs1−xPx/InAs1−ySby/InAs heterostructures grown by metalorganic chemical vapor deposition has been characterized using cross-sectional scanning tunneling microscopy. InAsxP1−x 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 InNyAsxP1−x−y alloy layers. Imaging of InAs1−xPx/InAs1−ySby superlattices reveals nanometer-scale clustering within both the InAs1−xPx and InAs1−ySby 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.