Temperature dependent electroluminescence in GaN and InGaN/GaN LEDs

We have investigated the electroluminescent properties of GaN and InGaN/GaN test structures grown on sapphire by MOCVD. Studies have been made over the temperature range from 370 to 80 K using a range of currents, pulse widths and duty cycles that reduce device heating. In homojunction structures, the complicated electroluminescence consists of several features while in the InGaN/GaN device the spectra consist of one broad feature. We have investigated how these features change as a function of temperature and have been able to relate these changes to the free carrier transport properties of the constituent materials and how these limit carrier transport to the recombination region. On the basis of this information, it is possible to suggest ways of maximising the electroluminescent efficiency of a particular device structure.