(Invited) Porous Silicon Dissolution Monitoring and Optical Constants Measurement Using in Situ Photoconduction in HF

Abstract

The progress of the chemical dissolution of porous silicon (PSi), formed from lightly-doped p-type silicon, in HF was monitored by recording in situ the photocurrent from a monochromatic illumination. The photocurrent is a signature of the optical transmission of the illumination in the substrate underneath PSi. The time corresponding to complete PSi dissolution is easily identified by a plateau of photocurrent. The effects of HF concentration, PSi porosity and PSi thickness were studied. The PSi dissolution rate is discussed. Using a model, the relations between the dissolution time, the porosity, and the absorption coefficient are elucidated. The effects of both PSi structure topology and quantum confinement on the optical absorption of PSi are discussed. The methods shown here allow the study of very high porosities while still having a clean hydrogen-terminated PSi surface and very good structural integrity, since PSi is never dried or exposed to air.