Thermal and non-thermal saturation effects in the output characteristic of UV-to-violet emitting (AlGaIn)N LEDs

UV‐to‐violet emitting (AlGaIn)N LEDs have been investigated with respect to the temperature‐dependence of the output power characteristics and non‐thermal rollover of the quantum efficiency at higher current densities. Analyzing MOVPE grown LED chips emitting in the 377 to 428 nm wavelength interval, the temperature sensitivity was found to increase and the output power to decrease with decreasing wavelength λ for λ < 400 nm. A sub‐linear increase of the output power with increasing injection current even in the absence of any thermal effects, i.e. a non‐thermal rollover of the quantum efficiency, was observed to be most pronounced for longer wavelength LEDs (λ > 400 nm). Furthermore, the transient temperature rise after turn‐on has been studied for differently packaged 377 nm LEDs, for which the temperature coefficient of the output power has been found to be particularly large. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)