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Presents a study that investigated homoepitaxial deposition of a GaN overlayer onto a bulk single-crystal GaN substrate using molecular beam epitaxy. Comparison of structural quality of deposited GaN overlayer with heteroepitaxially grown layers; Photoluminescence of bulk GaN and the deposited homoepitaxial GaN layer; Benefits for the development of benchmark values for the optoelectronic properties of GaN thin films.

Hexagonal InN layers were grown by molecular beam epitaxy and studied by high resolution electron microscopy and by photoluminescence spectroscopy. Inclusions of a few nanometers in diameter were found, which are among the smallest reported. Image simulation, beam sensitivity, and photoluminescence of the samples corroborate that these inclusions are indeed metallic indium. This letter provides evidence that nanoscopic metallic indium inclusions can be present in InN crystals and have a strong influence on its optical properties. [ABSTRACT FROM AUTHOR]

Employing the focal-series reconstruction technique in high-resolution transmission electron microscopy, we obtained true atomic resolution images of interfacial disorder within cation and anion sublattices across interfaces in an InGaSb/InAs heterostructure. This enabled independent quantitative mapping of changes in the In–Ga and As–Sb contents across interfacial regions ∼0.6 nm in width. A comparison of the cation and anion sublattice images revealed that intermixing at the InGaSb-on-InAs interface is confined to the In–Ga sublattice. Also, atomic scale roughness within the As–Sb sublattice of the InAs-on-InGaSb interface was discerned. This approach is general, permitting atomic-scale compositional analysis of heterointerfaces with two species per sublattice. [ABSTRACT FROM AUTHOR]

InN thin films have been grown epitaxially on GaN-buffered sapphire substrates by molecular-beam epitaxy at 500 °C. A high level of oxygen contamination in the growth chamber led to formation of In2O3 precipitates in the films. These precipitates were characterized in detail by transmission electron microscopy (TEM). The concentration of In2O3 was estimated to be less than 0.07 vol % in the present samples of oxygen content ∼0.5 at. %. Cross-sectional TEM investigations revealed that the precipitates adopt a preferred crystallographic orientation within the InN matrix, and show a characteristic diameter of ∼5 nm with average distance of ∼500 nm. These observations suggest the effective solubility of O in InN could be below 1 at. % at 500 °C. [ABSTRACT FROM AUTHOR]

Abstract: Zincblende and wurtzite phases of InN are found in InN epilayers deposited by molecular beam epitaxy on GaN buffers which were grown by metal organic chemical vapor deposition. Valence electron energy loss spectroscopy (VEELS) was applied to determine band transitions in both phases of InN. GaN buffer layers were used as VEELS reference. The chemistry and crystalline structure of the observed areas was recorded simultaneously to exclude a contribution from oxides and/or metal clusters or extended defects such as grain boundaries. At room temperature a band transition for wurtzite InN was found at and for zincblende InN at (1.4±0.2)eV that are ascribed to the fundamental bandgaps of the respective polytypes. Those values correlate well with recent results of various research groups measuring the bandgap in InGaN alloys with VEELS. [Copyright &y& Elsevier]

Abstract: Valence electron energy loss spectroscopy (VEELS) was applied to determine band transitions in wurtzite InN, deposited by molecular beam epitaxy on (0001) sapphire substrates or GaN buffer layers. The GaN buffer layer was used as VEELS reference. At room temperature a band transition for wurtzite InN was found at (1.7±0.2eV) and for wurtzite GaN at (3.3±0.2eV) that are ascribed to the fundamental bandgap. Additional band transitions could be identified at higher and lower energy losses. The latter may be related to transitions involving defect bands. In InN, neither oxygen related crystal phases nor indium metal clusters were observed in the areas of the epilayers investigated by VEELS. Consequently, the obtained results mainly describe the properties of the InN host crystal. [Copyright &y& Elsevier]