Drift mobility measurements in porous silicon

Modulated electroluminescence (EL) measurements performed on a series of porous silicon (PSi) diodes are presented. The maximum response time of the devices scales with the square of the PSi layer thickness and inversely with the applied forward bias voltage. These scaling results indicate that the maximum response time is a carrier transit time from which a drift mobility mu of 10(-4) cm(2)/Vs is deduced at room temperature. Time-of-flight transport measurements on PSi are in qualitative agreement with this value for mu; in addition, they identify mu as the electron mobility and show that transport is dispersive, in contrast to the interpretation of the modulated EL experiments.