Influence of Doping Density on the Current−Voltage Characteristics of p-Type Silicon in Dilute Hydrofluoric Acid

Abstract

The mechanism of p-type porous silicon formation in dilute hydrofluoric acid has been examined over a wide range of resistivities. The current−voltage curves show a negative potential shift as the resistivity of the silicon is reduced, a phenomenon that is explained in terms of a corresponding shift in the flat-band potential. Furthermore it is found that for all resistivities the flat-band potential is negative of the so called “Jps peak”, and an argument is presented that shows that this observation effectively disproves previous literature that has postulated that the “Jps peak” marks the transition between porous silicon formation and electropolishing. An observed decrease in the magnitude of the Jps peak for the two most heavily doped samples can be accounted for if the rate-determining step in PSi formation becomes the breaking of the Si−Si back-bonds, a process that should be potential dependent.