Thermal and nonthermal factors affecting the quantum efficiency of deep-ultraviolet light-emitting diodes

Abstract

The optical characteristics of AlGaN-based multiple-quantum-well (MQW) light-emitting diodes (LEDs) with peak wavelengths ranging from 265–340 nm were characterized over a wide current range. It was found that thermal effects due to self-heating can be largely eliminated by pulsing the LEDs with a duty cycle below 0.2%. The current-induced energy shift up to 850 A/cm2 was negligible in the deep-UV LEDs, indicating the lack of localization effects. The quantum efficiency of the LEDs increased monotonically at low currents and attained a low saturated value at high currents. This is in contrast to the efficiency rolloff behavior of typical InGaN-based LEDs resulting from carrier delocalization at high injection levels. The efficiency saturation of the deep-UV LEDs suggests that defects play an important role in both carrier injection and recombination processes. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)