A comparative study of the internal quantum efficiency for the green MQWs grown on sapphire and FS-GaN substrates

We observed the green MQWs grown on FS‐GaN substrates leading to less generation of dislocation, V‐defect, and stacking fault than those on sapphire by AFM and TEM. The temperature‐dependent PL spectral peak energies of the green MQWs grown on FS‐GaN substrates reveal more clear “S”‐shaped behaviors due to stronger carrier localization than those on sapphire substrates. Also, the green MQWs grown on FS‐GaN have the higher internal quantum efficiency (IQE) of 9 ∼ 12% in compared to those grown on sapphire at the same MQW thickness and wavelength of 530 ∼ 540 nm. These results will be due to the effects of the enhanced carrier localization and the reduced quantum confined stark effect (QCSE) by reason of the optical‐loss reduction as decreasing the defect density and the piezoelectric field reduction as decreasing the relaxation of strain. We could identify that the green MQWs grown on FS‐GaN substrates have the superior characteristics of the optics, structure, and surface to those on sapphire substrates. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)