Simultaneous determination of defect distributions and energies near InGaN/GaN quantum wells by capacitance-voltage measurement

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.