High-efficiency Si-gel-encapsulated GaN-based photonic crystal blue light-emitting modes

Abstract

Highly efficient Si-gel-encapsulated GaN-based blue light-emitting diodes were realized by introducing square-lattice photonic crystal patterns (a = 1200 nm) into their top layers. Absorptive three-dimensional fin ite- difference time-domain computations for a broad range of lattice constants (200 similar to 3000 nm) were investigated to optimize the enhancement of the light output. Integration sphere measurements were used to show that there are relative enhancements of similar to 35 % and similar to 70 % before and after encapsulation respectively with a dome-shaped Si gel. The achievable relative enhancement was estimated by using the ray-tracing method. In addition, the radiation from the encapsulated light-emitting diodes was found to be distributed over a relatively narrow angular spread.