Integration of Porous Silicon Interference Filters in Si-Photodiodes

A novel type of color-sensitive Si-photodiodes is presented Color-sensitivity is achieved by using porous silicon (PS) interference filters which were integrated in the p⁺-type part of conventional Si pn-junctions. These interference filters consist of PS layers with alternating high and low porosity, corresponding to low and high refractive inde-xes, respectively. Such structures can be fabricated very cheap and fast by varying the anodization current density during the anodic etching of the PS. In this way, we were able to realize Bragg-reflectors and Fabry-Perot filters whose transmission characteristics caused a strong modification of the photodiodes´ spectral response.