MORPHOLOGICAL STABILITY ANALYSIS OF POROUS SILICON FORMATION

Morphological stability analysis for the photoelectrochemical etching of n-type Si is performed, in which the stability of the back-illuminated Si-electrolyte interface is theoretically investigated. Both the transport of holes in the semiconductor and ions in the diffusion layer are considered, together with the electrochemical reaction and surface energy. The roles and the effects of the various parameters, such as applied potential, dopant concentration, current density, illumination intensity, surface energy, and electrolyte concentration, on the morphology of porous silicon are studied. The results show that porous silicon is formed when the dissolution process is controlled by the supply of holes in the semiconductor, and the density of porous silicon is a property which is both material- and process-dependent.