Reversible charging effects on optical properties of porous silicon

In our previous theoretical studies, through an effective medium approximat ion it was deduced that the effect of introducing charge is to decrease the absorption and coefficient of the material. In the present experimental st udies porous silicon samples have been charged, depending on the current in tensity, the intensity of the Photoluminescence Excitation response can be modulated in the energy range 1.5-2.6 eV. A decrease in the emission intens ity with an increase in charging current has been observed. This effect is reversible and the recovery time is found to be in the range of 4-6 min. Th e variation of charging effect with the thickness of porous silicon layers has also been studied. An increase in the lowering of the intensity with an increase in thickness has been observed. (C) 2001 Published by Elsevier Sc ience Ltd.