The recombination of excess carriers at a silicon-electrolyte interface

The recombination of excess carriers at the surface of a semiconductor depends on the surface potential in a bell-shaped manner (`Stevenson-Keyes curve¿). This holds in the case of silicon also if the surface is in contact with an electrolyte. To illustrate this dependence the recombination velocity is investigated by observing the photo-voltaic effect of a p-n junction alloyed to one surface of a thin silicon disc which is illuminated with non-penetrating light on the other side. The sensitivity of the photo effect is inversely proportional to the recombination velocity at the illuminated surface. If this surface is in contact with an electrolyte and if voltages of only a few tenths of a volt are applied between them, the sensitivity varies in a bell-shaped manner. The fact that the surface potential is influenced by the applied voltage can be proved by observing the surface photo effect between the silicon and electrolyte.