Nanoscale silicon microcavities for biosensing

We report the design and testing of a versatile biosensor exclusively using silicon. The device structure consists of a microcavity resonator made of various porous silicon layers. Porous silicon contains silicon nanocrystals that can luminesce efficiently in the visible, depending on the size and passivation conditions. When a luminescent porous silicon layer is inserted between two Bragg reflectors (also made of porous silicon), the broad luminescence band is altered and multiple and very narrow peaks are detected. The position of these peaks is extremely sensitive to a small change in refractive index, such as that obtained when a biological object is attached to the large internal surface of porous silicon. We have demonstrated a DNA sensor that displays appropriate sensitivity, selectivity and response speed. The device fabrication procedure and the results of extensive testing are presented. An extension of the DNA biosensor has been made to include the detection of viral DNA. This work will lead to the development of an all-silicon sensor array for the detection of biomacromolecules.