Electron Time-of-Flight Measurements in Porous Silicon

Transient photocurrent measurements are reported in an electroluminescent porous silicon diode. Electron drift mobilities are obtained from the data as a function of temperature. Electron transport is dispersive, with a typical dispersion parameter α≈ 0.5. The range of mobilities is 10−5 − 10−4 cm2Vs between 225 K amd 400 K. This temperature-dependence is much less than expected for multiple-trapping models for dispersion, and suggests that a fractal structure causes the dispersion and the small mobilities.