From Large-Size to Micro-LEDs: Scaling Trends Revealed by Modeling

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.