Conductivity in porous silicon

Admittance spectroscopy has been performed on Al dots deposited on porous Silicon grown on p+ substrates. They exhibit d.c. current-voltage characteristics of a metal-insulator-semiconductor structure containing a large concentration of localized states in the insulator. The admittance is composed of a frequency (ω) independent conductance while the reactance varies as ωs with s = 1. This strongly suggests that conduction through porous Silicon layers is governed by hopping between surface states