Mechanism of anodic electroluminescence of porous silicon in electrolytes

A mechanism of charge-carrier transfer from an electrolyte into porous silicon, which explains the efficient anodic electroluminescence of porous silicon, is proposed and analyzed in detail. It is shown that when a current flows through the interface, electrically active particles accumulate in the electrolyte - atomic hydrogen and oxygen, which with respect to porous silicon are efficient electron donors and accepters. Visible-range electroluminescence arises as a result of bipolar electron and hole injection from the electrolyte into high-resistance quantum-well crystallites of porous silicon. It is shown that the overall mechanism is the same for anodic and cathodic electroluminescence. This explains the well-known similarity of these two processes. The detailed physicochemical processes, which are the basis for anodic luminescence, are explained. (C) 1998 American Institute of Physics. [S1063-7826(98)01705-0].