Nitrate ion detection using AlGaN/GaN heterostructure-based devices without a reference electrode

Synchrotron-based XPS studies of AlGaN and GaN surface chemistry and its relationship to ion sensor behaviour

“…Functionalisation of the transistor surface by various means including nanorods [14], a metallic thin film [15] and a polymer membrane [16,17] has enabled the selective detection of chemical analytes or biological species. For AlGaN/GaN devices, the properties of the surface layer result in a linear drain current dependence with pH when operated with a reference electrode [18,19].…”

XPS/NEXAFS spectroscopic and conductance studies of glycine on AlGaN/GaN transistor devices

“…The presence of ions and/or dipoles on the surface induces an effective surface potential affecting the measured conductivity of the 2-DEG channel. We have recently shown that with appropriate PVC-based membranes these devices can be used to sense Hg 2+ and NO 3 ions in solution, with comparable or better performance when compared to existing portable ion sensor technologies [5,6].…”

Interdigitated Extended Gate Field Effect Transistor Without Reference Electrode

“…11 In recent years, many attempts have been investigated to replace the commercial reference electrodes, for example, by a solid-state planar on-chip reference electrode or a reference field-effect transistor. 11,12 However, despite these efforts, these methods suffer from poor performance, instability, short life time, and complex fabrication and integration with other microfabrication processes. [11][12][13] On the other hand, chemical sensors with interdigitated electrodes (IDEs) have significant advantages over other kinds of arrangements of electrodes: first,the possibility of easy labon-a-chip fabrication and integration, 14 second, the ability to monitor the resistivity and the permittivity of a solution 15 third, they have a shallow electric field penetration depth, which makes them sensitive to changes occurring close to their surface, and allows the use of thin sensing films for designing selectivity and sensitivity 15 and fourth, they offer a large variety of sizes, shapes and materials to address the particular requirements.…”