Electrical effects of DNA molecules on silicon field effect transistor

Much research has been devoted to the field of DNA detection for biotechnology and medical diagnostics. Conventionally, this has involved lab-scale large instruments such as fluorescent microscope, with DNA binding and tagging. Recently, however, the possibility of label-free, rapid, sensitive and miniaturized DNA detection electronically has attracted increasing interest in the field. To investigate the feasibility of DNA detection by the semiconductor field effect without tagging or binding agents, we studied the effects of DNA molecules directly on the gate oxide of field effect transistors (FET). DNA solution was deposited onto the gate region of conventional silicon FET devices without gate metal, and current-voltage measurements were performed. Our work showed that the presence of DNA molecules in an aqueous solution on the gate decreased channel current I_ds and increased threshold voltage. With increasing concentration in the solution, the threshold voltage increased monotonically. We observed that the channel current was reduced systematically during the hybridization of complementary DNA strands. The mechanism that induced the threshold voltage shift is attributed to the negative charges the DNA molecules carry and to changes in work function (Fermi energy). Our results showed the possibility that field effect transistors may provide a vehicle for a label-free, miniaturized and semiconductor-based DNA detector.