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.

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Metalorganic chemical vapor deposition was used to grow N-rich side GaNSb alloys under different growth conditions, and, for the first time, a considerable amount of Sb was incorporated into the GaNSb. The amount of Sb increased as the growth temperature decreased, but the maximal Sb content seemed to be limited by the solid solubility of Sb in GaN. Absorption spectroscopy of the GaNSb revealed a strong absorption band below the band gap of GaN. The below-band gap absorption extended to 0.8 eV, which makes GaNSb a promising material to serve as an infrared absorption layer on GaN.

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An anodic etching technique for selective lateral wet etching of n-doped GaN without the photo-assistance was described. Ndoped GaN was successfully etched with 0.3 M oxalic acid at 40V.