An ideal method to quantify the internal quantum efficiency (IQE) of radiation for condensed-matter placed outside an integrating sphere (φ-configuration) is demonstrated by showing the data for a freestanding GaN crystal using improved omnidirectional photoluminescence (ODPL) spectroscopy, Kojima et al. [J. Appl. Phys. 120, 015704 (2016)]. The crystal is optically coupled with the sphere through a pinhole fabricated on the sphere, and thus ODPL with φ-configuration gives IQE because the light-escaping cone for the crystal defines the observable photoluminescence owing to the large absorption and crystal thickness. This nondestructive ODPL configuration is applicable to large size crystals or semiconductor wafers.
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