Measurement of extraction and absorption parameters in GaN-based photonic-crystal light-emitting diodes

The light extraction efficiency of photonic-crystal (PhC) light-emitting diodes (LEDs) relies on the competition between the PhC extraction and dissipation mechanisms of the guided light within the LED. This work presents the experimental determination of the PhC extraction length of each guided mode and the absorption coefficient of the active region (AR) and quantum wells (QWs) from the observation of the LED far-field emission using a high-resolution angle-spectrum-resolved measurement. The angular and spectral linewidths of the extracted guided modes reveal, depending on the spectral range, the modal extraction length of the PhCs, the AR absorption length, or a combination of both. Modes with a high confinement with the QWs presented a shorter absorption length compared with their extraction length by a shallow surface PhC (95-nm-deep), meaning that the AR absorption was a more efficient mechanism than the PhC extraction. The measured modal extraction length of the shallow surface PhC varied in the ra...