Photoelectronic properties of porous silicon

It is shown that the introduction of a porous structure into single-crystal Si produces substantial changes in the photoelectronic properties. The porous Si (PS) layer is formed by anodization of p-type Si wafers in a HF solution. The photoconduction cells used in this study consists of a semitransparent thin Au film, PS, Si substrate, and Al ohmic contact. The photoconductive behavior of PS is characterized by an extremely high dark resistivity, a definite photosensitivity for visible light, and an intrinsic bias voltage dependence of the spectral response. These properties, which are interpreted to be the result of a band-gap widening in PS, provide further support of the assumption that the visible luminescence of PS is explained by the band scheme.