The electrochemical etching of crystalline silicon in hydrofluoric acid based solutions has been found to produce a porous layer, termed porous silicon (PS), which is found to exhibit photoluminescence (PL) and electroluminescence (EL) in the visible region. While the luminescence mechanism is the subject of much debate, the potential for this material is enormous as it could usher in a new generation of silicon-based optoelectronic devices. An electrolytic cell capable of producing luminescent layers of porous silicon over large area silicon wafers has been designed and fabricated. The stability of the PL of PS after subjection to standard microelectronic processing steps, namely thermal oxidation, ion implantation, and reactive ion etching has been investigated. Changes in the PL intensity as well as shifts in the PL wavelengths observed after processing support the quantum confinement and surface states theories for the luminescence. These results also support the possibility of integrating PS into standard silicon integrated circuit processing. For the study of EL, Au/PS Schottky, ITO/PS heterojunction and PS pn junction diodes have been fabricated. EL efficiencies in the range of 10~5 to 10"7 have been determined for these devices. The diodes typically exhibit extremely high series resistance and ideality factor values. These results are direct consequences of the large non-planar surface area of PS yielding poor electrical contacts and high surface state densities. These factors need to be drastically improved to obtain efficient EL in PS devices. A unique process capable of obtaining 5 u.m wide lines of luminescent porous silicon in close proximity to device quality polished silicon is also presented.
Library of Congress Subject Headings
Silicon--Optical properties; Electroluminescence; Optical materials; Luminescence
Department, Program, or Center
Center for Materials Science and Engineering
Seiferth, Frederick, "Light emission from silicon" (1994). Thesis. Rochester Institute of Technology. Accessed from
RIT – Main Campus