PHOTOELECTRIC PROPERTIES OF SELF-SUPPORTING POROUS SILICON

We present transient and steady-state photocurrent data, measured in a special sample holder on a self-supporting porous silicon (PS) sandwich structure. Although the value of the drift mobility is difficult to find, we have estimated on the basis of the time of flight (TOF) technique the trap controlled value of mobility-lifetime product (mu(D)tau(D)) and from the steady-state photocurrent we have deduced recombination controlled (mutau)ss value. Surprisingly (mutau)ss<mu(D)tau(D). Charge collection is very low (about 1%) even for electric field F almost-equal-to 10(5) V/cm. However, the ''schubweg'' = mutauF is (for eta almost-equal-to 10% and F = 10(8) V/cm) about 1 mum, much more than the quantum size dimensions (2-5 nm).