This study investigates the distribution of highly-directional far-field emission on GaN-based ultrathin microcavity light-emitting diodes (uMCLEDs) with photonic crystals (PhCs). The ultrathin 550 nm cavity, PhC lattice constant of 370 nm, and hole depth of 250 nm in the GaN PhC uMCLED provide near single guided mode extraction and a pattern of high directionality radiation. Angular-spectral-resolved electroluminescence measurements reveal photon-band structure agreement with the fundamental mode effective refractive index dispersion curve. In addition, GaN PhC uMCLED increase the output power extraction efficiency by 145.9% (similar to 2.46x) compared with GaN non-PhC uMCLED, and a directional far-field emission pattern at half intensity of nearly +/- 15 degrees. (C) 2010 American Institute of Physics. [doi:10.1063/1.3459970]