Highly Sensitive pH Sensing Using an Indium Nitride Ion-Sensitive Field-Effect Transistor

We demonstrated an ultrathin (~10 nm) ifndium nitride (InN) ion-sensitive field-effect transistor (ISFET) for pH sensing. The native indium oxide formed on the InN surface functions as a chemical binding layer with a high pH sensitivity, while the strong surface electron accumulation of InN along with the ultrathin conduction channel results in a large ion-induced surface potential to current transconductance. The ultrathin InN ISFETs were characterized to show a gate sensitivity of 58.3 mV/pH in the pH range of 2-12, a current variation ratio of 4.0%/pH, a resolution of less than 0.03 pH, and a response time of less than 10 s.