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 he terostructures grown by gas-source molecular beam epitaxy and in InAs1-xPx/ InAs1-ySby/InAs heterostructures grown by metalorganic chemical vapor depos ition has been characterized using cross-sectional scanning tunneling micro scopy. InAsxP1-x alloy layers are found to contain As-rich and P-rich clust ers with boundaries formed preferentially within ((1) over bar 11) and (1(1 ) over bar 1) crystal planes. Similar compositional clustering is observed within InNyAsxP1-x-y alloy layers. Imaging of InAs1-xPx/InAs1-xSby superlat tices reveals nanometer-scale clustering within both the InAs1-xPx and InAs 1-ySby alloy layers, with preferential alignment of compositional features in the [<(1)over bar 12>] direction. Instances are observed of compositiona l 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 interfa ce. (C) 1999 American Vacuum Society. [S0734-2101(99)15204-7].