Specific features of electrical transport in anisotropically nanostructured silicon

Electrical transport in layers of porous silicon obtained by electrochemical etching of (110)-oriented single-crystal silicon wafers of p type was studied. It was found that the lateral conductivity and photoconductivity of the layers along the [1 10] crystallographic axis substantially exceed those along the [001] axis. The results obtained are explained in terms of the effective-medium model, which takes into account the presence of potential barriers at boundaries of anisotropically shaped silicon nanocrystals. The exponential dependence of the conductivity of porous silicon on the square root of the applied voltage is interpreted in terms of the Poole-Frenkel effect.