B. Gelloz et A. Bsiesy, CARRIER TRANSPORT MECHANISMS IN POROUS SILICON IN CONTACT WITH A LIQUID-PHASE - A DIFFUSION PROCESS, Applied surface science, 135(1-4), 1998, pp. 15-22
Citations number
30
Categorie Soggetti
Physics, Applied","Physics, Condensed Matter","Chemistry Physical","Materials Science, Coatings & Films
The carrier transport mechanisms in reverse-biased p-type porous silic
on in contact with an aqueous electrolyte are investigated under polar
isation conditions where efficient visible electroluminescence can be
observed. A photo-induced current is obtained by electron-hole pairs g
eneration simultaneously in the porous silicon skeleton and in the und
erlying silicon substrate using illumination at suitable wavelengths.
Experiments are based on the analysis of the impedance response of thi
s system, on the evolution of the photo-induced current vs. potential
as a function of the porous layer thickness and on the time-evolution
of the electroluminescence (EL) signal, The results of these experimen
ts suggests the following points: (1) The analysis of the impedance re
sponse shows that the potential drop occurs primarily in the silicon s
ubstrate across the space charge region. (2) Only the carriers generat
ed in the space charge region give rise to a photo-induced current. (3
) The electrons which are photo-generated in the space charge region a
re accumulated in the initially depleted porous skeleton as can be evi
denced by a visible EL emission. In the light of these results the ele
ctron transport mechanisms in the porous silicon skeleton are clarifie
d, The major conclusion is that the liquid-impregnated porous silicon
skeleton is under equipotential conditions and that the substrate-supp
lied electrons penetrate the porous layer by a diffusion process. The
relation between these findings and the high EL efficiency shown by th
is system is also discussed. (C) 1998 Elsevier Science B.V. All rights
reserved.