LUNG-HAN PENGLu, C.-Y.C.-Y.LuWu, W.-H.W.-H.WuWang, S.-L.S.-L.Wang2009-03-182018-07-062009-03-182018-07-06200500036951http://ntur.lib.ntu.edu.tw//handle/246246/146017https://www.scopus.com/inward/record.uri?eid=2-s2.0-28344449716&doi=10.1063%2f1.2103423&partnerID=40&md5=8b6c8237ff7b966855cc095f40de9470We report the formation of gallium nitride (GaN) microcavities by manipulating a photoenhanced oxidation rate difference between the polar and nonpolar crystallographic planes of GaN. When immersed in a buffered acetic (C H3 COOH) electrolyte of pH∼6.2 at room temperature, it is shown that the photo-oxidation can proceed at a rate that is one order of magnitude slower on the nonpolar plane of {1 1- 00}GaN than on the polar plane of {000 1- }GaN due to the reduced surface field action. Gallium nitride microcavities bounded by optically smooth {1 1- 00} and {1 1- 03} facets can thus be preferentially formed on the c -plane sapphire substrate after dissolving the oxide layer. The optical properties of these GaN hexagonal cavities reveal characteristic peaks of whispering gallery modes in resonance with the GaN band edge emission spectrum. A typical cavity Q factor of 103 is observed in these GaN microcavities due to a reduced optical scattering loss in the wet chemical reaction process. © 2005 American Institute of Physics.application/pdf288205 bytesapplication/pdfen-USElectrolytes; Oxidation; pH effects; Sapphire; Band edge emission; Microcavities; Photoenhanced oxidation; Gallium nitridejournal article10.1063/1.21034232-s2.0-28344449716http://ntur.lib.ntu.edu.tw/bitstream/246246/146017/1/14.pdf