Optimizing the external light extraction of nitride LEDs

In modern GaN-based light-emitting diodes (LEDs) structures, total internal reflection (TIR) limits light extraction, and consequently, overall efficiency of the light source. Proper chip and package material combinations as well as surface property modifications offer the opportunity to reduce the luminous flux lost due to TIR and absorption. Different sepa-ration techniques are taking influence on substrate surface properties and thus on light extraction improvement. Imple-menting all these factors in a flexible ray tracing model and applying effective mathematical optimization, helps to refine a chip design in a fast and accurate way to achieve a significant increase of the light extraction. Based on experimental data and ray trace modeling, the effects of chip size scaling, surface roughness and encapsulation on light extraction val-ues will be demonstrated.