Pulse Current Electrochemical Deposition of Silicon for Porous Silicon Capping to Improve Hardness and Stability

This paper presents a method to improve the stability of porous silicon structures by electrochemical deposition of silicon capping. Porous silicon is formed by pulse electrochemical etching, followed by pulsed current electrochemical deposition, to provide a uniform silicon capping layer on the porous structure. The capping layer thickness and hardness increase with deposition time. The variation of strain in the porous structure is also observed with varying silicon capping layer thickness. Silicon capping of 4 mu m was sufficient to protect porous silicon from aging effects on their spontaneous emission, while a capping of 7.2 mu m causes a 40 nm redshift on the spectrum. (C) 2008 The Electrochemical Society. [DOI: 10.1149/1.3049861] All rights reserved.