The improved performance of a bottom photonic crystal (PC) light‐emitting diode (LED) is analyzed based on internal quantum efficiency (ηint) and light‐extraction efficiency (ηex). The bottom PC is fabricated by anodized aluminum oxide nanopatterns and InGaN quantum wells (QWs) are grown over it. Transmission electron microscopy images reveal that threading dislocations are blocked at the nanometer‐sized air holes, resulting in improved optical emission efficiency of the QWs. From temperature‐dependent photoluminescence measurements, the enhancement of ηint is estimated to be 12%. Moreover, the enhancement of ηex is simulated to be 7% by the finite‐difference time‐domain method. The fabricated bottom PC LED shows a 23% higher optical power than a reference, which is close to the summation of enhancements in ηint and ηex. Therefore, the bottom PC improves LED performance through higher optical quality of QWs as well as increased light extraction.
The efficiency of a light-emitting diode (LED) is limited because a large amount of generated light is confined inside due to total internal reflection. It is well known that light extraction from LEDs can be enhanced by using photonic crystal. However, the underlying physical mechanisms for increased emission are still largely unknown. In this work, we used the finite difference time domain method to analyze the photonic crystal (PC) LED with disordered air holes. The light extraction efficiency of disordered PC was nearly equivalent to that of ordered PC with the same pattern periodicity. This result supported the idea that the increased light extraction of PC LED was mainly due to the scattering, which is irrelevant to photonic band structure.
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