Temperature effects on optical properties and efficiency of red AlGaInP-based light emitting diodes under high current pulse pumping.

In this paper, current-dependent emission spectra and efficiency measured on the same AlGaInP red light-emitting diode (LED) pumped with the current pulses of very different durations are recorded. This enabled for the first time distinguishing between high-carrier concentration and self-heating effects on the efficiency decline at high current magnitudes. The electron leakage to the p-side of the LED structure, which is the major mechanism of the efficiency reduction, is found to rise substantially when the device self-heating starts to develop. As a result, in comparison to continuous-wave excitation, driving the LED with sub-microsecond current pulses allows suppressing the device self-heating and, eventually, increasing the operating current by an order of magnitude without noticeable efficiency losses. Based on the reduced ABC-model, neglecting Auger recombination, the light extraction efficiency, injection efficiency, and internal quantum efficiency of the LED are estimated, suggesting light extraction to be the most critical factor for the overall efficiency of the LED. The coupled spectral/power LED characterization using the variable-duration current pulse pumping is found to be an effective approach for analyzing mechanisms of the device operation. [ABSTRACT FROM AUTHOR]