Highly spatial resolved PL spectroscopy of single dislocations in InGaN/GaN quantum well structures

GaN based heterostructures normally show quite high dislocation densities. The impact of the dislocations on the performance of optoelectronic devices is still unclear. With our confocal microscope, we study single threading dislocations for samples with a dislocation density below 107 cm-2. The impact of threading dislocations on the optical properties of GaN bulk crystals is well known: The dislocations act as nonradiative recombination centers, and the shift of the near band edge emission due to the stress dipole around the dislocation core can be detected by highly spectral resolved photoluminescence (PL) spectroscopy. We now study the impact of single dislocations on the optical properties of InGaN/GaN quantum well structures. By simultaneous detection of the PL signal of both the InGaN quantum well and the GaN barriers, the variation of the quantum well signal can explicitly be attributed to single dislocations which are identified by the GaN emission. The effects in the quantum well are studied in dependency of temperature and excitation density