Electrical features of the metal-thin porous silicon-siliconstructure

Abstract

This paper considers a theoretical model of the metal-tunnelinterface layer-thin porous silicon-p-Si structure. A diffusion-driftequation at the appropriate boundary conditions is solved to clarify amechanism of the carriers' transport. The voltage drop distribution along thestructure is calculated by solving the equations under the condition ofcontinuity of the vector of the electrostatic induction. The obtainedanalytical expressions allow one to analyse the contribution of the interfacelayer, porous silicon and surface electron states to the electrical behaviourof the structure. Some parameters of the model are defined from the comparisonof experimental I-V and C-V characteristics with theoretical valuesfor the Pd-porous silicon (60% of porosity)-p-Si structures havingdifferent thicknesses of porous silicon layers. The defined barrier heighteφ0 ranged from 0.45 to 0.47 eV, the interface layer consisted ofmainly the native oxide achieved up to 3.0 nm and did not depend on the timeof Si electrochemical etching. The evidence that part of the voltage drops onthe surface electron states is ensued by comparing the experimental highfrequency C-V curves with steady-state I-V curves. Thickening of theporous silicon layer results in a shift in the energetic band of the surfaceelectronic states.