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We report the electrical characteristics of vertical and lateral type light emitting diodes (LEDs) grown with CrN buffer layer. The LED with CrN buffer showed lower reverse leakage current than the reference sample grown with conventional low-temperature GaN buffer. It was also observed that the density of open core screw dislocation was smaller by one order of magnitude, which was thought to relate to the leakage current of devices. The vertical type LED fabricated by chemical etching of CrN buffer showed lower series resistance, lower turn-on voltage, and larger light output power than those of the conventional LEDs. [ABSTRACT FROM AUTHOR]

Microphotoluminescence spectroscopy is used to investigate local strain in GaN films grown on c-sapphire with CrN buffer, where the CrN buffer is partly etched. Biaxial compressive strain dominates GaN films grown on CrN buffer/c-plane sapphire. The emission energies of D0X, FXA, and FXA-1LO emission lines shift gradually from a high value to a low one, as the excitation laser beam scans from the unetched side of the sample to the etched side, while the emission intensities show only a slight change. No cracking occurs in the GaN film during etching except a change in bending of the detached part of the GaN film from convex to concave as determined by surface profiler. Both the lattice parameter and the energy position of the bound exciton emission peaks from a completely detached GaN are almost the same as those reported for strain-free GaN. The line width of the (0002) ω scan of a GaN film is narrowed from 352 to 331 arc sec through detaching presumably due to decrease in bending. Those properties suggest that gradual lattice strain relaxation takes place in GaN layers grown on CrN buffer as etching of CrN buffer proceeds and that the chemical lift-off enables to detach a GaN film from a sapphire substrate without generating defects. [ABSTRACT FROM AUTHOR]

Stepwise cross-sectional crystallographic measurement was performed on the stress-induced void (SIV) of copper interconnect and it was possible to investigate the three-dimensional crystallographic structures near the submicron scale void. The void mainly happened at a triple junction of grain boundaries and there were at least two grains with high biaxial elastic modulus near the triple junction. The preferred site for the SIV could well be understood by considering the elastic anisotropy of each grain and the grain boundary type. [ABSTRACT FROM AUTHOR]

We report significant reduction of threading dislocations in GaN films grown by hydride vapor phase epitaxy on AlN/sapphire templates by employing CrN nanoislands on the AlN. High quality GaN films with very small twist mosaic as well as small tilt mosaic have been grown on the AlN/sapphire templates, which had small tilt but very large twist mosaic. The CrN nanoislands were formed by nitridation of a thin Cr film deposited by sputtering on the AlN/sapphire template, where the AlN/sapphire template was prepared by metal organic vapor phase epitaxy. The full width at half maximum values of x-ray rocking curves from the GaN film with the CrN were 114, 209, and 243 arc sec for (0002), (10-12), and (11-20) reflections, respectively, while those of the GaN film without the CrN were 129, 1130, and 1364 arc sec, respectively. Evaluation of total dislocation density of the GaN films by plan view transmission electron microscopy revealed that the dislocation density was reduced to 2.7×108 from 6.4×109 cm-2 by employing the CrN nanoislands. The CrN nanoislands play a key role in reducing the threading dislocations by masking the propagation of dislocations as well as by bending the dislocations. [ABSTRACT FROM AUTHOR]

The grain growth which occurs during the self-annealing in copper electrodeposits was investigated by in situ observation with an electron backscattered diffraction technique. From these observations, it was found that a newly created twin was initiated on the front interface of growing twin and that the transverse direction for the growth was <110>. Most of the twins had the Σ3 twin boundary of {111}<110>. The formation of the twin and its peculiar growth direction could be explained quite well based on the hypothesis that the growth front interface is one of the {111} planes. [ABSTRACT FROM AUTHOR]