A blue resonant cavity light emitting diode with a 50% Al-content crack-free GaN/AlGaN distributed Bragg reflector is reported. The structure shows excellent optical properties and the benefits of the cavity structure are clearly seen in the narrowed spectral emission and the output power increase when compared with our conventional LEDs. The output power values are found to be typical for light emitting diodes grown by molecular beam epitaxy indicating that the device performance is not degraded by the relatively larger lattice mismatch between the Al0.5Ga0.5N/GaN distributed Bragg reflector and the In0.15Ga0.85N/GaN active region.