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 grown on InP substrates by atomic layer molecular beam epitaxy at relatively low temperatures (330 degrees C < T < 400 degrees C). Moreover, we study the effect of the introduction of an intermediate InSb/InP buffer layer grown by molecular beam epitaxy. The studies were carried out by TEM and HRTEM, to investigate the densities and nature of the defects and the accommodation mechanism between the two types of layers which have a large lattice mismatch (10.4%). Results show a high defect density at the interface vicinity whatever the growth method employed, with or without buffer layers, but better quality layers are obtained as growth proceeds. The prevailing type of defects are threading dislocations and stacking faults for both types of samples, but the introduction of the intermediate layers leads to the formation of two types of complex three-dimensional defects, consisting in crystal misorientations, that induce an anomalous growth of the InSb layer leading to different growth rates and the formation of pyramidal or truncated pyramidal hillocks on the surface. In this case scanning electron microscopy and Raman analysis were also performed to study the influence of the defects on surface morphology and confirm their structure. Moreover, anisotropy of the stacking fault distribution is noticed in this sample: the density for [1(1) over bar0$]-(111)A slip planes is higher than for the [110]-(111)B slip planes. Strain due to large lattice mismatch is relieved. in both types of samples by the generation of a pure edge-type misfit dislocation array.