General trends in scaling dimensions of a circular‐shaped flip‐chip light‐emitting diode (LED) are studied by coupled electrical‐thermal‐optical simulations. Advanced chip design is considered, providing high efficiency of light extraction through the top surface of the LED die. The simulation model accounts for such important effects, as current crowding near metallic electrodes, thermal and non‐thermal efficiency droop caused by Auger recombination, and surface recombination at the edges of the LED active region. Interplay and competition of the mechanisms is demonstrated in a wide range of operating current densities and chip dimensions varied from tens to hundreds of micrometers. It is shown that surface recombination, which is especially important in small‐size LEDs, is the major mechanism controlling evolution of the LED characteristics under the chip size variation. The impact of surface recombination on LED characteristics is predicted to weaken at high current densities typical for operation of micro‐LEDs due to shortening of carrier life time in the active region. Advantages of micro‐LEDs are discussed on the basis of the simulations.

The paper considers surface recombination at the free active region surface as the mechanism of carrier losses which has not yet been discussed with regard to III‐nitride LEDs despite of its evident importance for AlGaInP‐based light emitters. Using advanced thin‐film and triangular volumetric chip designs reported in literature as prototypes, we have demonstrated by simulation a noticeable impact of surface recombination on the wall‐plug efficiency of InGaN‐based LEDs. Various types of LEDs whose efficiency may be especially affected by surface recombination are discussed. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)

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Practically all III‐nitride light emitting diodes (LEDs) suffer from the efficiency rollover that occurs at high electric currents in the devices and limits their performance. At the moment, the mechanisms responsible for the rollover are not yet confidently identified despite the crucial importance of this problem for the LED production. On the basis of simulation, we suggest that the Auger recombination is a likely mechanism, producing the efficiency reduction at high currents. Using an empirically estimated Auger recombination coefficient, we argue for significance of this mechanism under practical operation conditions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A hybrid approach to modeling of electrical, optical and thermal processes in state-of-the-art light-emitting diodes (LEDs) is described in detail. The advantages of the approach are demonstrated with reference to an interdigitated multipixel array (IMPA) chip design recently suggested to improve the LED performance at high-current operation. Such an LED, consisting of a hundred single-pixel light sources integrated on a common substrate, has a rather complex multi-scale geometry challenging for a coupled analysis of the device operation. The hybrid approach is found to enable coupled simulation of the current spreading, heat transfer and light emission in the IMPA LED at a modest demand of computer resources and computing time. Specific features of the IMPA LED operation are discussed in terms of modeling and compared with those of a conventional square-shaped LED. The impact of current crowding on the uniformity of light emission from the dice of both types is examined. A dramatic difference in the series resistance of the IMPA and square-shaped LEDs is explained on the basis of current spreading analysis. The active region overheating is found to be a critical factor eventually limiting the output optical power of the square LED. Good agreement between the theoretical predictions and observations is demonstrated, which justifies the use of the hybrid approach.