Introduction to the Special Issue on “Simulation of GaN-based Light-Emitting Diodes”

Abstract

The Nobel Prize in Physics 2014 was awarded jointly to I. Akasaki, H. Amano and S. Nakamura “for the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources”. Their invention of GaN-based LEDs has generated intense worldwide research and development activities, not only for general lighting applications, but also in many other areas, such as displays, sensing, biotechnology, and medical instrumentation. Growing efforts are currently directed towards modeling and simulation of these devices. To a large extent, these efforts are driven by a mysterious phenomenon, the so-called efficiency droop. The expected high energy efficiency of GaN-based LEDs is only observed at low injection current and low light power. With rising current, injected electron-hole pairs disappear increasingly in non-radiative recombination processes, thereby reducing the fraction that delivers photons (internal quantum efficiency). Still unclear is the specific non-radiative mechanism that dominates this efficiency droop. The two leading explanations are Auger recombination and electron leakage, respectively, in possible combination with other effects. However, very few direct measurements of either mechanism are published thus far, none of which establishes a dominating magnitude. Thus, manypublications on the efficiency droopbase their quantitative claims on themodeling and simulation of efficiencymeasurements. Several contradicting models have been shown to reproduce the same type of measured efficiency characteristics. But in any given case, only one such model, if any, can be correct. This dilemma represents a severe but valuable challenge to the computational electronics community.