Quantum Efficiency in Multi-quantum well InGaN/GaN Light-emitting Diodes with Electroluminescence Characteristics

The temperature dependence of the electroluminescence spectra of InGaN/GaN multi-quantumwell light-emitting diodes (LEDs) has been investigated over a range of temperatures and currents. The presence of localization effects in the active InGaN layers can be deduced from the observed considerable blue shifts of the electroluminescence emission peak with increasing temperature in the low-temperature region. Exciton-phonon couplings in the active layer are also observed at low temperatures. The electroluminescence intensity was measured to determine the internal quantum efficiency of the LEDs as a function of temperature. When the temperature decreases from room temperature to 170~200 K, the electroluminescence intensity increases due to a reduction in the nonradiative recombination, and the internal quantum efficiency is improved. At T < 170 K, the electroluminescence intensity is reduced significantly. This reduction of the electroluminescence intensity mainly results from the low carrier capture efficiency in the active layer due to the high Mg activation energy, the electron-hole separation in multi quantum wells, and the high internal piezoelectric field. However, in the case of LEDs using a narrow barrier, the electroluminescence intensity is reduced slightly at low temperatures. Therefore, in order to measure the internal quantum efficiency by using the temperature dependence of the electroluminescence spectra in LEDs, one must carefully consider the effects of carrier injection at low temperature. KCI Citation Count: 1