AFM and SEM Study on Crystallographic and Topographical Evolutions of Wet-Etched Patterned Sapphire Substrate (PSS): Part III. Cone-Shaped PSS Etched in H2SO4 and H3PO4 Mixture at Various Temperatures

摘要

The effect of etching temperature (473-543 K) on the crystallographic and topographical evolutions as well as the etching rate of crystallographic planes of cone-shaped patterned sapphire substrate (PSS) etched in both H2SO4-based (H2SO4:H3PO4 = 5:1 at volume ratio) and H3PO4 etchants was systematically studied. For H2SO4-based etchant, higher temperature favors larger etching rate ratio of slant planes (S-1{1 (1) over bar 05}, S-3 {4 (5) over bar 138}, S-4 {1 (1) over bar 012}, and S-5 {(1) over bar 1037} planes) to c-plane, thus leading to smaller filling factor (FF) of patterns; the Arrhenius activation energy (E-a) of etching reactions for various crystallographic planes follows the order: E-a (c) E-a (S-1) E-a (S-3) E-a (S-4). For H3PO4, higher temperature favors smaller etching rate ratio of slant planes (S-1 {1(1)over bar05} and S-6 {1 (1) over bar 108} planes) to c-plane and larger FF of patterns; the E-a follows the order: E-a (S-1) E-a (S-6) E-a (c). This work will contribute to elucidating the etching mechanism and fabricating optimized PSS for enhanced performance of light emitting diodes. (c) The Author(s) 2017. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.