Temperature dependence of internal quantum efficiency of radiation for the near-band-edge emission of GaN crystals quantified by omnidirectional photoluminescence spectroscopy

Internal quantum efficiency of radiation (IQE) for the near-band-edge (NBE) emission of freestanding-GaN crystals was observed by omnidirectional photoluminescence spectroscopy at various temperatures between 12 K and 300 K. A photoluminescence quenching ratio (Rq), defined by a spectrally integrated NBE emission obtained at 300 K to that obtained at 12 K, showed a lower value (2%) comparing with the IQE value (5.5%) for the GaN with the free electron concentration of 1 × 1017 cm−3 under cw photo-pumping density of 13 W cm−2. This difference arises from the nonlinear relationship between IQE and the external quantum efficiency owing to the photon recycling effect.