Role of inversion layer formation in producing low effective surface recombination velocities at Si/liquid contacts

Photoconductivity decay lifetimes have been obtained for NH4F(aq)-etched Si (111) and for air-oxidized Si(111) surfaces in contact with solutions of CH 3OH or tetrahydrofuran (THF) containing either ferrocene(+/0) (Fc(+/0)), bi s(pentamethylcyclopentadienyl) Fe+/0, or I-2. Si surfaces in contact with e lectrolytes having Nernstian redox potentials > 0 V versus the standard cal omel electrode exhibited low effective surface recombination velocities reg ardless of the different surface chemistries, whereas those exposed only to N-2(g) ambients or to electrolytes containing mild oxidants showed differi ng rf photoconductivity decay behavior depending on their different surface chemistry. The data reveal that formation of an inversion layer, and not a reduced density of electrical trap sites on the surface, is primarily resp onsible for the long charge-carrier lifetimes observed for Si surfaces in c ontact with CH3OH or THF electrolytes containing I-2 or Fc(+/0). (C) 2000 A merican Institute of Physics. [S0003-6951(00)03642-1].