This work “Development of GaN Resonant Cavity LEDs (RCLEDs)” for short distance high speed data communication using plastic optical fibre (POF) was conducted in the Tyndall National Institute (previously known as National Microelectronics Research Centre) and was presented to the National University of Ireland for the degree of Doctor of Philosophy. During the time of this publication (autumn, 2002), it was the first approach on monolithically grown resonant cavity LEDs on GaN based semiconductor material. Using the fabricated RELEDs a data transmission rate of 100 MBits/sec over 100 meters was achieved through a 1 mm core POF. For some devices under constant current biasing, the intensity was observed to fluctuate irregularly accompanied by correlated variations in the voltage. The emission from the RCLED was focused through a GaAs wafer onto a Vidicon camera. Flashes from point sources on the RCLED surface were observed, indicating that short-lived, highly localized "hot spots" formed that generated pulses of thermal radiation. This happens from metal migration into nanopipes present in this material.