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The transmission electron microscopy technique is employed to explain the structural, as well as the optical properties of the AlGaN/AlGaN multiple quantum well (MWQ) structures. The dislocation arrays and other properties of the two different buffer layers present in the system are also analyzed.

Low temperature cathodo- and photoluminescence is used for studying nonpolar a-plane GaN films grown by using epitaxial lateral overgrowth. Monochromatic cathodoluminescence imaging has shown that various emission features are correlated with the microstructure of the film and the peak energy of the basal-plane stacking fault emission is blueshifted in the wing relative to the window region.

The transmission electron microscopy technique is employed to explain the various structural properties of the wurtzlike scandium gallium nitride films that are grown by the molecular beam epitaxy method. An increase in the Sc concentration in the films is shown to lead to a significant increase in the c, as well as the a lattice parameters.

A series of GaN films are grown by metalorganic vapor phase epitaxy on nitrided sapphire by using an initial annealed low-temperature nucleation layer (LT-NL), without using any conventional threading dislocation (TD) reduction methods. Coalesced films have a high TD density with a spatially random TD arrangement, but it is altered into a lower TD density, spatially clustered arrangement during growth.

Highly conductive modulation doped composition graded p-AlGan/(AlN)/GaN multiheterostructures is studied and the abruptness of the AlGaN/AlN/GaN interfaces is determined by using high resolution x-ray diffraction and x-ray reflectometry. The overall voltage drop can be reduced by substituting the p-GaN layer in a light emitting diode (LED) with an AlGaN/GaN multiheterostructure and the improved current spreading on the p-side of LEDs with integrated AlGaN/GaN multiheterostructures is proved by [micro]-electroluminescence.

A series of heteroepitaxial nonpolar a-plane GaN films with different densities of dislocations and basal plane stacking faults are explored to gain insight into the defect densities which relate to x-ray diffraction (XRD) data obtained from the rapid evaluation of the structural quality of thin films. No direct correlations are observed between defect densities and any measured (XRD) parameter but a specific analysis of each individual broadening factor could be used to identify the structural imperfections dominating XRD data.

The article presents the impact of water curvature on the full width at half maximum (FWHM) of the x-ray rocking curves ([omega]-scans) observed in the gallium nitride and other crystalline thin films. The dislocation densities of the films is shown to be approximately proportional to the square of the [omega]-FWHM value.

The accurate Poisson's ratio value determined for a typical c-axis-oriented GaN film grown by metal-organic vapor-phase epitaxy depostion is reported. The Poisson's value is observed to be lower than most calculated values, attributed to the presence of stain-relieving edge dislocations in GaN sample.

The elastic properties of ScN films on Si were studied by determining macroresidual strains in a series of ScN films using high-resolution x-ray diffraction (HRXRD). The values of 0.188+ or minus 0.002 and 270 plusmn 25 obtained for Possion's ratio and Young's modulus respectively were comparable to those previously determined for (100)-oriented ScN, despite the elastic anisotropy of ScN.