AC impedance studies on metal/nanoporous silicon/p-silicon structures

Abstract

Alternating current (AC) impedance measurements have been performed on 10𝜇𝜇𝜇𝜇−15 𝜇𝜇𝜇𝜇 thick porous silicon layers on a (100) p-type silicon (p(+)Si) substrate with the aluminium (Al) top electrode in a sandwich configuration in the range of 20 Hz to 1 𝑀𝑀Hz and in the temperature ranging between 152 K−292 K. The ac conductivity sac was found to increase with frequency f according to the universal power low: sAf=acs where the exponent s is a frequency and temperature dependent quantity. Hopping process is found to be dominant at low temperatures and high frequencies while a thermally activated free band process is responsible for conduction at higher temperatures. Capacitance is found to decrease with frequency but increase with temperature. Frequency dependence of loss tangent is observed with a temperature dependent minimum value.