MICROSTRUCTURE OF PYRAMIDAL DEFECTS IN INSB LAYERS GROWN BY ATOMIC LAYER MOLECULAR-BEAM EPITAXY ON INP SUBSTRATES

We report on the structural characterization of epitaxial InSb films g rown on InP substrates by atomic layer molecular beam epitaxy at relat ively low temperatures (330 degrees C < T < 400 degrees C). Moreover, we study the effect of the introduction of an intermediate InSb/InP bu ffer layer grown by molecular beam epitaxy. The studies were carried o ut by TEM and HRTEM, to investigate the densities and nature of the de fects and the accommodation mechanism between the two types of layers which have a large lattice mismatch (10.4%). Results show a high defec t density at the interface vicinity whatever the growth method employe d, with or without buffer layers, but better quality layers are obtain ed as growth proceeds. The prevailing type of defects are threading di slocations and stacking faults for both types of samples, but the intr oduction of the intermediate layers leads to the formation of two type s of complex three-dimensional defects, consisting in crystal misorien tations, that induce an anomalous growth of the InSb layer leading to different growth rates and the formation of pyramidal or truncated pyr amidal hillocks on the surface. In this case scanning electron microsc opy and Raman analysis were also performed to study the influence of t he defects on surface morphology and confirm their structure. Moreover , anisotropy of the stacking fault distribution is noticed in this sam ple: the density for [1(1) over bar0$]-(111)A slip planes is higher th an for the [110]-(111)B slip planes. Strain due to large lattice misma tch is relieved. in both types of samples by the generation of a pure edge-type misfit dislocation array.