Fabrication of antireflective SiC surface using plasma etching with self-assembled nanopattern

1. Fabrication of antireflective SiC surface using plasma etching with self-assembled nanopattern Y. Ou1,2, A. Argyraki1, and H. Ou1 1. DTU Fotonik, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark 2. Light Extraction ApS, Diplomvej 373, DK-2800 Kgs. Lyngby, Denmark yiyu.ou@lightextraction.com Characterization and results Introduction • Merits of SiC as substrate in LEDs : • Small lattice mismatch with GaN (3.5%) • Can be conductive which allows for a fabrication of vertical device structure • Excellent thermal conductivity, preferred in high power LEDs • Challenge: • Low light extraction efficiency and large internal reflection loss due to high refractive index value of 6H-SiC (n=2.68) • Method to enhance the light extraction: • Fabrication of antireflective structures (ARS) on SiC substrate 5 nm 7 nm 3 nm 9 nm 11 nm 13 nm Nano-islands size distribution Fabrication process • Surface reflectance and transmittance were measured in a spectral range from 350-785nm by using an integrating sphere • Lower reflectance and higher transmittance are observed after introducing SiC ARS 200nm (a) Thin metal film deposition; (b) Rapid thermal processing; (c) Reactive-ion etching 5 nm 7 nm 200nm 200nm 3 nm Summary • Pseudo-periodic ARS have been fabricated on SiC substrate by using self-assembled nanopattern • Density and average size of ARS can be controlled by tuning the deposited Au film thickness and thermal processing conditions • Suppressed surface reflectance and enhanced light transmittance can be obtained by fabricating ARS with various size • This method is time-efficient, low cost, and scalable 9 nm 11 nm 13 nm 1µm 1µm 1µm SEM: Au nano-islands (made from different Au film thickness) 5 nm 7 nm 3 nm 200nm 200nm 200nm 200nm 200nm 200nm 9 nm 11 nm 13 nm Reference Y. Ou, et al., Opt. Lett. 37, 3816, 2012. Y. Ou, et al., Opt. Mater. Express 3, 86, 2013. SEM: SiC ARS (made from different Au film thickness)