Electrically pumped grating-assisted resonant-cavity Light-Emitting Diodes

The Grating-Assisted Light-Emitting Diode, an LED design for high brightness based on a resonant cavity containing ID or 2D periodically corrugated layers (grating), is subject of this presentation. The diffractive properties of the wavelength scaled periodic grating integrated in one or both of the interfaces of the resonant-cavity, can redirect the laterally propagating resonant guided mode to an extractable direction. Because of the high power fraction in these guided modes, the use of such gratings can result in a higher extraction efficiency than a homogeneously layered RCLED, in which the trapped guided mode is a loss of power. In this scope, a generally applicable rigorous electromagnetic analysis based on the Coupled Wave Theory for diffractive gratings, has been developed to calculate the extraction efficiency of spontaneous emission in a periodically corrugated layer structure. This general model has been applied to a GA-RCLED emitting at 980 nm. The structure consisting of a hybrid bottom-emitting cavity with metallic grating and bottom DBR mirror, shows simulated efficiencies of over 40%. Electrically pumped devices have been processed. Experimental data and simulation results, such as polarization selective emission, spectral behavior and efficiency are compared and discussed.