INFLUENCE OF WETTABILITY ON ANODIC BIAS INDUCED ELECTROLUMINESCENCE IN POROUS SILICON

Anodic oxidation in hydrochloric (HCl) acid and chemical dissolution in hydrofluoric (HF) acid solutions of porous silicon (PS) layers obtained from lightly doped p-type substrates have been investigated. It is shown that the wettability of PS, which is a highly hydrophobic and organophilic material, strongly affects its electroluminescence (EL) during anodic oxidation and its chemical etch rate in HF solutions. When the solutions do not penetrate the pores, a very weak EL intensity is obtained and the chemical etch rate in HF is found to be very slow. However, when the solutions infiltrate the pores, both the EL intensity and chemical etch rate are dramatically increased. In the first case, only the top surface of the porous layer is accessible to the liquids while in the second case the whole volume of the material and its vast inner surface are involved.