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

• Published in: Physica status solidi. A, Applications and materials science Applications and materials science, 2018-05, Vol.215 (10), p.n/a
• Main Authors: Konoplev, Sergey S., Bulashevich, Kirill A., Karpov, Sergey Yu
• Format: Article
• Language: English
• Subjects: Augers; Carrier lifetime; chip design; Computer simulation; Current density; device simulation; efficiency; Light emitting diodes; Micrometers; Scaling; Thermodynamic efficiency; Trends
• ISSN: 1862-6300; 1862-6319
• DOI: 10.1002/pssa.201700508

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. Using selfconsistentelectrical‐thermal‐optical simulations, this paper analyzes general trends in variation of main light‐emitting diode's (LED) characteristics under wide‐range scaling of the device dimensions. Surface recombination at the open edges of LED active region, Auger recombination initiated by high electron and hole density in the active region, and temperature dependence of recombination coefficients are found to be the major factors controlling the LED efficiency. The revealed scaling trends are interpreted qualitatively in terms of a simple ABC‐model, though quantitative predictions require elaborated numerical modeling.