Abstract
AbstractChemically modified Field Effect Transistor (ChemFET) sensor for ammonium (NH$ ^+_4 $) ions was developed from AlGaN/GaN High Electron Mobility Transistor (HEMT) structures (NH$ ^+_4 $‐ChemHEMT). The sensor consists of a HEMT device with non‐metallized gate, which was coated with a polyvinyl chloride (PVC) membrane enriched with ammonium ionophore (Nonactin). The AlGaN/GaN NH$ ^+_4 $‐ChemHEMT with gate width of 100 μm and gate length of 100 μm exhibited a constant sensitivity of 55.5 mV/pNH$ ^+_4 $ for NH$ ^+_4 $ concentration in the range from 10–5 M to 10–2 M. The NH$ ^+_4 $ concentration detection limit was 5.4 × 10–6 M, which is approximately one order of magnitude lower compared to Si based insulator gate ChemFETs. The sensor exhibited also sufficiently long storage lifetime, indicating the strong adhesion of the PVC membrane to the GaN(0001) surface. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
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