Enhancement of the quality of InAsSb epilayers using InAsSb graded and InSb buffer layers grown by hot wall epitaxy

We have investigated the structural and electrical properties of InAsxSb1−x epilayers grown on GaAs(0 0 1) substrates by hot wall epitaxy. The epilayers were grown on an InAsSb graded layer and an InSb buffer layer. The arsenic composition (x) of the InAsxSb1−x epilayer was calculated using x-ray diffraction and found to be 0.5. The graded layers were grown with As temperature gradients of 2 and 0.5 °C min−1. The three-dimensional (3D) island growth due to the large lattice mismatch between InAsSb and GaAs was observed by scanning electron microscopy. As the thicknesses of the InAsSb graded layer and the InSb buffer layer are increased, a transition from 3D island growth to two-dimensional plateau-like growth is observed. The x-ray rocking curve measurements indicate that full-width at half-maximum values of the epilayers were decreased by using the graded and buffer layers. A dramatic enhancement of the electron mobility of the grown layers was observed by Hall effect measurements.

Source:IOPscience

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Self-ordering of metal-free phthalocyanine on InAs(100) and InSb(100)

The adsorption and surface ordering of metal-free phthalocyanine (H2PC) on InAs(100)(4 × 2)/c(8 × 2) and InSb(100) c(8 × 2) is investigated using scanning tunnelling microscopy (STM) and synchrotron based photoelectron spectroscopy. The two systems show structural similarities; at submonolayer coverage the preferred adsorption site of H2PC is on top of the In rows, and above 1 monolayer and after thermal treatment the first molecular layer is ordered in a densely packed '× 3' structure observed with both low energy electron diffraction and STM.

The electronic properties and the surface bonds of the two systems are quite different: the InAs–H2PC interface is semiconducting after room temperature adsorption but becomes metallic upon thermal treatment whereas InSb(100)–H2PC is semiconducting at all preparations. These differences are reflected in pronounced differences in the C 1s line shape between the two systems. N 1s core level spectra from both surfaces reveal deprotonation of the molecules, i.e. the central hydrogen atoms are lost upon thermal treatment.

Source:IOPscience

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Exploration of the inherent magnetoresistance in InSb thin films

The depth-dependent electrical properties of InSb thin films grown on GaAs substrates result in an inherent magnetoresistance in the layers. For certain applications it is important to be able to manipulate this effect controllably. This paper demonstrates both experimentally and theoretically that the magnitude of the magnetoresistance can be dramatically changed by epilayer design. We show that the inclusion of a doped region in part of the layer structure allows the inherent magnetoresistance to be changed by a factor of 40.

Source:IOPscience

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Structural and morphological features of ultrathin epitaxial InSb films in AlAs matrix

This work presents results of the investigation of structural and morphological features of epitaxial InSb layers in the AlAs matrix. Our research group used transmission electron microscopy (TEM). The specimens were grown by molecular beam epitaxy and prepared in the cross section (110) and plan view foils (100). We found a formation of the embedded epitaxial layer of solid solution InxAl1-xSbyAs1-y in the AlAs matrix during precipitation of In and Sb on the AlAs surface. The embedded layer had continuous area (wetting layer) and islands. The study revealed two types of islands in the epitaxial layer the first having coherent interfacing with the matrix lattice and the second a relaxed island. We estimated concentration of In, Sb in the solid solution by the indirect method. We used the method of geometric phase to analyze the distribution of misfit dislocation cores on the interface. Every misfit dislocation was formed by two close 600-dislocations with the Burgers vectors like a /2 <110>. The sum Burgers vector of the dislocation pair was in the plane of the interface.

Source:IOPscience

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