Stabilization of porous silicon electroluminescence by surface passivation with controlled covalent bonds

Stabilization of electroluminescence (EL) from nanocrystalline porous silicon (PS) diodes has been achieved by replacing silicon-hydrogen bonds terminating the surface of nanocrystalline silicon with more stable silicon-carbon (Si-C) and silicon-oxygen (Si-O-C) bonds without significant effects on the electrical properties. The surface modification is performed by a thermal treatment of partially and anodically oxidized PS sample at about 90 degreesC with organic molecules: 1-decene, ethyl undecylenate, or n-caprinaldehyde. The porous silicon device whose surface has been modified with stable covalent bonds shows no degradation in the EL efficiency and EL output intensity under dc operation for several hours. The improved stability can be attributed to the high chemical resistance of Si-C and Si-O-C bonds against current-induced surface oxidation associated with the generation of nonradiative defects. (C) 2003 American Institute of Physics.