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The distributions, densities and energies of defects near InGaN/GaN quantum wells in blue light-emitting diodes were simultaneously determined by utilizing capacitance–voltage (C–V) measurements. By combining the modulation frequency dependency, temperature dependency and C–V depth profiling with additional laser illumination, the densities and the locations of the defective layers could be determined. The relative defect densities of the devices were directly compared by monitoring the magnitude of the frequency dependence. This frequency dependency varies distinctly as the sample temperature changes. The activation energies of defects are then determined by analyzing the frequency dependency of C–V with temperature. We found that three different defects states were formed in a low-temperature-grown un-doped GaN (LT-GaN) layer inserted under the active layer. The activation energies of those defects were determined to be 3.96, 12.1 and 45.9 meV. The formation of additional defects states in the active layers induced by the insertion of LT-GaN layer was also observed.

We report the electrical properties of single-walled carbon nanotube bundles aligned between two electrodes with a gap of 8 µm by the alternating current dielectrophoresis method. The resistance increased exponentially as the number of structural defects increased from the oxygen plasma treatment. However, no noticeable change was observed in the carrier concentration and tube–tube interaction. The resistance dependence on the plasma treatment time was explained on the basis of the localization of electron states at defect sites. The aspects of the defects were examined by measuring the effects of ammonia adsorption on the conductance of the device.