Efficient light-emitting diodes with radial outcoupling taper at 980- and 630-nm emission wavelength

We have investigated efficient light outcoupling from light- emitting diodes (LEDs) by introducing lateral tapers. The concept is based on light generation in the very central area of a circularly symmetric structure. After propagating between two highly reflecting mirrors light is outcoupled in a tapered mesa region. By proper processing we achieve quantum efficiencies of almost 40% for outcoupling via a planar surface or quantum and wallplug efficiencies of 52% and 48%, respectively, for encapsulated devices. Neglecting reabsorption, approximative equations yield optimum design parameters.