Nb2O5 as a High-k Alternative to Ta2O5 for Enhanced Gate Gain on Field-Effect Biosensors

Arrays of ion-sensitive field-effect transistors play a crucial role in many applications including cancer monitoring. In these applications, high-k pH-sensing dielectrics, such as Ta<inf>2</inf>O<inf>5</inf>, are utilized to enhance both gate gain and Nernstian gain. This study reports that Nb<inf>2</inf>O<inf>5</inf>, a sister material to Ta<inf>2</inf>O<inf>5</inf> that is commonly used in electrolytic capacitors, can be deposited and annealed at temperatures compatible with Al vias, where such vias are frequently employed in sensing arrays. Electrical characterization of metal-oxide-semiconductor stacks and constant-capacitance pH-measurements using electrolyte- insulator-semiconductor samples demonstrate that Nb<inf>2</inf>O<inf>5</inf> offers the possibility of achieving both high gate gain and high Nernstian gain.