Light-induced porous silicon photoluminescence quenching

The photoluminescence quenching of lightly doped p-type porous silicon in c ontact with aqueous acidic electrolytes is investigated under reverse-bias conditions. A complete and reversible quenching of the light emission is ob served under infra-red illumination of the samples. This quenching is assig ned to the injection into the porous layer of the electrons which are photo generated in the substrate. The quenching features are studied as a functio n of the electron concentration in the porous layer, which is varied either by changing the intensity of the light excitation that generates the minor ity carriers in the silicon bulk or, at a given light intensity, by changin g the electrolyte composition. In the latter case, the electron concentrati on is dependent on the electrochemical reactions which take place at the po rous layer surface and which partly consume the injected electrons. It is s hown that the amount of injected electrons directly determines the magnitud e of the quenching and the associated spectral changes. It is concluded tha t the assumption of an enhanced charge carrier separation by the electric h eld as a possible quenching mechanism can be ruled out, and that the experi mental results rather support the hypothesis that the quenching involves an Auger recombination process. (C) 1999 Elsevier Science B.V. All rights res erved.