Temperature dependence of the quantum efficiency in green light emitting diode dies

The electroluminescence of GaInN/GaN multiple quantum well light-emitting diode dies is analyzed at variable low temperatures. We compare the external quantum efficiency of three dies of nominally identical structure but strongly different RT performance at 520 nm. For all dies, the external quantum efficiency increases as the temperature is lowered. A maximum is reached for all near 158 K while for lower temperatures as low as 7.7 K, the efficiency continuously drops. The low-temperature efficiency is the lowest for the highest performing die at RT. The peak energy exhibits a blue shift from RT to 158 K followed by a red shift for lower temperatures. In the same low-temperature range, a secondary emission peak appears near 390 nm that resembles a donor-acceptor pair transition. The pronounced efficiency maximum is tentatively assigned to competition of carrier transport properties and the non-radiative lifetime in the active region.