V-defects play an important role in carrier recombination in polar InGaN quantum wells (QWs). Here we report a study of V-defects in QWs emitting from 410 to 570 nm performed by time-resolved near-field optical spectroscopy. In V-defect regions, the radiative carrier lifetime is longer and the nonradiative - shorted than in defect free regions, showing strong spatial variations of the internal quantum efficiency (IQE). The areas with the low IQE, however, are limited to regions just above the dislocations (~2% of the total sample area) showing that the nonradiative recombination at dislocations is not a major factor determining the IQE.
Efficient high-power operation of light emitting diodes based on InGaN quantum wells (QWs) requires rapid interwell hole transport and low nonradiative recombination. The transport rate can be increased by replacing GaN barriers with that of InGaN. Introduction of InGaN barriers, however, increases the rate of the nonradiative recombination. In this work, we have attempted to reduce the negative impact of the nonradiative recombination by introducing thin GaN or AlGaN interlayers at the QW/barrier interfaces. The interlayers, indeed, reduce the nonradiative recombination rate and increase the internal quantum efficiency by about 10%. Furthermore, the interlayers do not substantially slow down the interwell hole transport; for 0.5 nm Al0.10Ga0.90N interlayers the transport rate has even been found to increase. Another positive feature of the interlayers is narrowing of the QW PL linewidth, which is attributed to smoother QW interfaces and reduced fluctuations of the QW width.
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