Morphological stability analysis for the photoelectrochemical etching
of n-type Si is performed, in which the stability of the back-illumina
ted Si-electrolyte interface is theoretically investigated. Both the t
ransport of holes in the semiconductor and ions in the diffusion layer
are considered, together with the electrochemical reaction and surfac
e energy. The roles and the effects of the various parameters, such as
applied voltage, dopant concentration, current density, illumination
intensity, surface energy, and electrolyte concentration, on the morph
ology of porous silicon are studied. The results show that porous sili
con is formed when the dissolution process is controlled by the supply
of holes in the semiconductor, and the density of porous silicon is b
oth material- and process-dependent.