High-efficiency semiconductor resonant-cavity light-emitting diodes: a review

An overview of highly efficient resonant-cavity light-emitting diodes is presented. First, the basics of dipole emission in planar cavities are reviewed. From these, a number of design rules are derived. We point out some guidelines for comparison of high-efficiency light-emitting diodes, and use these to review the state-of-the-art devices in different material systems and at different wavelengths. We also discuss some advanced techniques based on gratings or photonic crystals to improve the efficiency of these devices.