High-field modulated ion-selective field-effect-transistor (FET) sensors with sensitivity higher than the ideal Nernst sensitivity.

Lead ion selective membrane (Pb-ISM) coated AlGaN/GaN high electron mobility transistors (HEMT) was used to demonstrate a whole new methodology for ion-selective FET sensors, which can create ultra-high sensitivity (-36 mV/log [Pb]) surpassing the limit of ideal sensitivity (-29.58 mV/log [Pb]) in a typical Nernst equation for lead ion. The largely improved sensitivity has tremendously reduced the detection limit (10 M) for several orders of magnitude of lead ion concentration compared to typical ion-selective electrode (ISE) (10 M).