Numerical investigation of purcell enhancement of the internal quantum efficiency of GaN-based green LED structures

GaN-based green light-emitting diode (LED) structures suffer from low internal quantum efficiency (IQE), known as the “green gap” problem. The IQE of LED structures is expected to be improved to some extent by exploiting the Purcell effect. In this study, the Purcell effect on the IQE of green LED structures is investigated numerically using a finite-difference time-domain simulation. The Purcell factor of flip-chip LED structures is found to be more than three times as high as that of epi-up LED structures, which is attributed to the high-reflectance mirror near the active region in the flip-chip LED structures. When the unmodified IQE is 20%, the relative enhancement of IQE can be greater than 50%, without utilizing the surface-plasmon coupling effect. Based on the simulation results, the “green gap” problem of GaN-based green LEDs is expected to be mitigated significantly by optimizing flip-chip LED structures to maximize the Purcell effect.