Extended gate REFET (Reference-FET) using 2D h-BN sensing layer for pH sensing applications

Though ISFET (Ion-Sensitive Field Effect Transistor) has been widely used in measuring pH or other ions in electrolyte, one of main challenges it faces is its large volume of fluidic reference electrode. The use of REFET is one approach to address the above issue where a pH inert material such as hydrophobic polymer is used as sensing layer. However, REFETs with polymer sensing film may suffer from instability and non-uniformity. In this letter, an extended gate ISFET with 2D hexagonal boron nitride (h-BN) as sensing layer is proposed and demonstrated as a REFET. The device with as-exfoliated 2D h-BN flake shows a low pH sensitivity of less than 5 mV/pH and low drift around 0.50 mV/hour. All these suggest 2D h-BN a highly potential candidate to be used in making a stable and high performance REFET.