A new four-terminal hybrid silicon/organic field-effect sensor device

We present the first demonstration of a novel field-effect device which has two channels: one formed in an organic semiconductor and the second in silicon. The channels are coupled such that one gates the other, with the organic channel exposed to air such that it is able to interact with chemicals in the ambient. This device represents a major improvement over both the traditional CHEMFET (which is a silicon MOSFET with the gate uncovered to be chemically sensitive) (Janata, 1989), and an organic transistor chemical sensor (Crone et al., 2001). While the device we developed can also function as a traditional CHEMFET, one of the more powerful sensing modes occurs when the two channels are coupled and changes in the organic channel carrier density in response to analyte delivery are reflected as changes in the current through the silicon channel. Another unique sensing mode, which appears to be the most sensitive, is designated as the chemical memory mode. In this mode analyte molecules result in trapped charges in the organic semiconductor which change the threshold voltage of the silicon FET. We have observed a response in the chemical memory mode that is between 10 and 100 times more intense than the response in the traditional CHEMFET mode