title: Design and fabrication of high-index-contrast self-assembled texture for light extraction enhancement in LEDs.
abstract: We developed a high-index-contrast photonic structure for improving the light extraction efficiency of light-emitting diodes (LEDs) by a self-assembly approach. In this approach, a two-dimensional grating can be non-lithographically integrated on the top of virtually any types of LEDs with controlled structural parameters and material indices. As a proof of concept, our designed photonic structure was implemented on a GaAs double heterojunction LED. Using numerical electromagnetic simulations, we explored the effects of the structural parameters (the grating period, layer thickness and material indices) on the device performances, followed by fabrication through a self-assembled porous alumina as a template. Device simulation and experimental results indicate that an optimized high-index-contrast (a-Si / air) grating obtains a much larger efficiency increase than using a low-index SiO2 grating. In addition, the devices maintain a Lambertian radiation pattern with the self-assembled grating. This technique provides an effective and low-cost method for improving LED efficiency.
authors: Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA. shengx@mit.edu
authors: Xing
authors: X
authors: Sheng
authors: Lirong Zeng
authors: LZ
authors: Broderick
authors: Juejun
authors: J
authors: Hu
authors: Li
authors: L
authors: Yang
authors: Anat
authors: A
authors: Eshed
authors: Eugene A
authors: EA
authors: Fitzgerald
authors: Jurgen
authors: J
authors: Michel
authors: Lionel C
authors: LC
authors: Kimerling