Anodization of undoped amorphous silicon by electrical injection of holes

Electrochemical etching of undoped hydrogenated amorphous silicon layers in HF solutions was performed in the "injection regime". Holes necessary for the anodization of silicon are produced by electrical injection from a p(+) back contact rather than by p-type doping of the material. We have found t hat there is no measurable injection of electrons from the electrolyte. The injection regime is responsible for a new macro-instability, with the form ation of large channels across the film which hinder the elaboration of a m icroporous silicon layer. (C) 1999 Elsevier Science Ltd. All rights reserve d.