AFM and SEM Study on Crystallographic and Topographical Evolutions of Wet-Etched Patterned Sapphire Substrate (PSS): Part II. Cone-Shaped PSS Etched in H2SO4 and H3PO4 Mixture with Varying Volume Ratio at 230 degrees C

摘要

Here we present a systematic study on crystallographic and topographical evolutions as well as etching rates of crystallographic planes of cone-shaped patterned sapphire substrate (PSS) etched in H2SO4 and H3PO4 mixture with a wide range of volume ratios (H2SO4:H3PO4 = 1:0, 5:1, 3:1, 1:1, 1:3, and 0:1) at 230 degrees C. The Miller indexes of four major exposed crystallographic planes were determined as S-1 {1 (1) over bar 0 5}, S-3 {4 (5) over bar 1 38}, S-4 {1 (1) over bar 0 12}, and S-6 {1 (1) over bar 0 8}. The etching rates of crystallographic planes follow the order S-1 S-3 S-4 c plane for H2SO4 and H3PO4 mixtures as well as S-1 S-6 c plane for H3PO4. A larger volume ratio (higher H2SO4 concentration) favors a higher etching rate of c-plane and conversely lower etching rates of S-1-, S-3-, and S-4-planes, thus causing a larger filling factor with the largest filling factor of 0.93 obtained at the volume ratio of 5:1. This work will contribute to revealing the etching mechanism and fabricating optimized PSS for enhanced performance of light-emitting diodes. (c) The Author(s) 2017. Published by ECS. All rights reserved.