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The morphology and electrical properties of doped semi-insulating gallium nitride (GaN) epilayers have been studied. It was found that doping-induced improvement of the insulating properties of GaN epilayers with increased level of doping with carbon or iron is limited by the accompanying deterioration of surface morphology. The character of impurity-related morphology development is different for the two dopants. It is established that the co-doping with carbon and iron allows planarity of the GaN surface to be retained along with a significant improvement of insulating properties of epilayers. [ABSTRACT FROM AUTHOR]

Abstract: The growth features of GaN nanorods on patterned c-sapphire substrates with a regular microcone array having a different density and base diameter in the ranges of (1-5) × 107 cm-2 and 2.5-3.5 μm, respectively, are investigated. The kinetics is studied and the selective-growth regimes are determined for single GaN nanorods with a diameter of 30-100 nm at the vertices of microcones under radically lower growth rates on their slopes. The effect of the configuration of microcones, the substrate temperature, the roughness of the initial surface, and the presence of indium as a surfactant on the degree of growth selectivity is investigated. [ABSTRACT FROM AUTHOR]

AlGaN/AlN/GaN and InAlN/AlN/GaN structures with 2D electron gas have been grown on sapphire substrates by metal-organic vapor-phase epitaxy. The suppression of the parasitic conductivity of buffer GaN layers was provided either by intentionally raising the density of edge dislocations or by doping with iron (GaN:Fe). It was shown that using GaN buffer layers with a better crystal perfection and more planar surface results in the electron mobility in the 2D channel for carriers becoming 1.2-1.5 times higher. [ABSTRACT FROM AUTHOR]

The influence of propane present in a reactor at various stages of GaN growth by metalorganic vapor phase epitaxy (MOVPE) on sapphire substrates on the character of epitaxial process and the properties of epilayers has been studied. Doped GaN epilayers with carbon concentration 5 × 10 cm characterized by high crystalline perfection, an atomically smooth surface, and electric breakdown voltage above 500 V at a doped layer thickness of 4 μm have been obtained. [ABSTRACT FROM AUTHOR]

We report on fabrication and studies of composite heterostuctures consisting of an Al0.55Ga0.45N/Al0.8Ga0.2N quantum well and surface Al nanoislands, grown by plasma-assisted molecularbeam epitaxy on c-sapphire substrates. The influence of a substrate temperature varied between 320 and 700ºC on the size and density of the deposited Al nanoislands is evaluated. The effect of Al nanoislands on decay kinetics of the quantum well middle-ultraviolet photoluminescence has been investigated by time resolved photoluminescence. The samples with the maximum density of Al nanoislands of 108 cm-2 and lateral dimensions in the range of 100-500 nm demonstrated shortening of the photoluminescence lifetime, induced by interaction of the emitting quantum well and the plasmonic metal particles. [ABSTRACT FROM AUTHOR]

III-N blue LED structures with active regions based on InGaN nanoislands are studied. The structures are grown by metalorganic vapor-phase epitaxy (MOVPE) on GaN layers deposited by various methods for the initial formation of an epitaxial layer. It is shown that, due to strong carrier localization in narrow-gap InGaN nanoislands, the electroluminescence efficiency is independent of the crystal perfection of the material. [ABSTRACT FROM AUTHOR]

A new method of forming InGaN/GaN nanostructures emitting in the long-wavelength green spectral range is proposed and implemented. The method is based on growing a thin InGaN layer over nanosized pits formed in situ by etching a locally AlN-masked GaN layer in a hydrogen-containing atmosphere. [ABSTRACT FROM AUTHOR]

It is suggested that the analysis of the short-wavelength edge of intrinsic photoluminescence in diluted GaN xAs1 − x alloys at room temperature be used to study the specific features of the energy dependence of the density of states in the conduction band. It is found that, in the GaN xAs1 − x alloys with x ≥ 0.002, this dependence is inconsistent with the model of the anticrossing band and suggests that there are extra states. These states are thought to be the states formed in nitrogen clusters and interacting with the conduction band. The energy of these states is at least 1.45 eV above the top of the valence band. [ABSTRACT FROM AUTHOR]

Epitaxial gallium nitride (GaN) structures have been manufactured by the lateral overgrowth technology, whereby GaN epilayers are grown in stripe windows on a partly masked initial GaN layer. It is established that in addition to the traditional orientation of stripes across the c axis, the process is also possible for the stripes oriented at 45° relative to this axis. In this case, two lateral overgrowth processes in mutually perpendicular directions can be performed, which would significantly reduce the relative area of imperfect material formed over windows in the mask. [ABSTRACT FROM AUTHOR]