Current progress of omnidirectional photoluminescence spectroscopy for the quantification of quantum efficiency of radiation in GaN crystals

The current progress of the omnidirectional photoluminescence (ODPL) spectroscopy for quantifying the internal quantum efficiency (IQE) of a near-band-edge emission in GaN will be reviewed. IQE reflects the concentration of nonradiative recombination centers and deep impurities such as carbon. A prototype of the ODPL spectroscopy was proposed with “2pi-configuration”. However, the 2pi-configuration has a limitation on the sample size due to the integrating sphere used. Therefore, "phi-configuration" was introduced, where the crystal was placed outside the sphere. This allows to cool the sample down to 12 K in vacuum, and to perform a mapping experiment of IQE across the GaN wafers.