Chemically sensitive field-effect transistors (ChemFETs) have been extensively investigated and widely applied as sensors for various chemical and biological analytes [1] since their invention by Bregveld in 1970 [2]. Main advantages of ChemFETs over conventional ion-selective electrodes (ISE) consist in small dimensions, fast response and possibility of integration in the sensor array or microfluidic and/or electronic systems (a lab-on-chip concept). Moreover, ChemFETs are relatively easy for mass production. Typically, SiO₂/Si heterostructures are used for constructing ChemFET sensors, although organic ChemFETs are extensively investigated as well [1c]. Recently, there is a growing interest in ChemFETs based on wide-bandgap semiconductors, such as diamond, SiC and GaN. The GaN-based ChemFET sensors combine advantages of superior electrical parameters with high thermal and chemical stability. Because a GaN crystal features similar surface chemistry properties as those of metal oxides, its surface can readily be modified resulting in formation of films selectively recognizing analytes of interest. Moreover, the GaN-based ChemFET is transparent to visible light. Therefore, processes occurring on the transistor surface can simultaneously be monitored spectroscopically. Pristine and chemically modified FETs as well as high electron mobility transistors (HEMTs) based on the GaN or the AlGaN heterostructures have already been applied as sensors for determination of pH [3], anions [4] and proteins [5], as well as various gases and vapours [6]. Herein, an overview of operating principles, fabrication procedures and applications of ChemFETs for sensing purposes will be given. Development of cyclodextrin polymer coated high electron mobility transistor, based on AlGaN/GaN/sapphire heterostructure, will be presented and application of the polymer coated heterostructures for detection of benzene derivatives will be discussed. It will be shown that a-cyclodextrin polymer film modified HEMT structure can selectively detect p-nitrophenol, especially in its anionic (p-nitrophenolate) form. Moreover, attempts to develop a sensor, based on heterostructures coated by molecularly imprinted polymers of functionalised cyclodextrins, for sensing of compounds of biological importance will be described.

Bibliography

1. (a) A. K. Covington, Pure Appl. Chem. 66 (1994) 565; (b) J. Janata, Electroanalysis 16 (2004) 1831; (c) H. E. Katz, Electroanalysis 16 (2004) 1837.
2. P. Bergveld, IEEE Trans. Biomed. Eng. 17 (1970) 70.
3. G. Steinhoff, M. Hermann, W. J. Schaff, L. F. Eastman, M. Stutzmann, M. Eickhoff, Appl. Phys. Lett. 83 (2003) 177.
4. Y. Alifragis, A. Georgakilas, G. Konstantinidis, E. Iliopoulos, A. Kostopoulos, N. A. Chaniotakis, Appl. Phys. Lett. 87 (2005) 253507.
5. B. S. Kang, F. Ren, L. Wang, C. Lofton, W. W. Tan, S. J. Pearton, A. Dabrian, A. Osinsky, P. P. Chow, Appl. Phys. Lett. 87 (2005) 023508.
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2. Piezomicrogravimetric chemosensor for determination of selected alkaloids with dedicated porphyrin polymer film as recognition unit
3. Molecularly imprinted polymer (MIP) chemosensors for surface plasmon resonance (SPR) and differerntial pulse voltammetry (DPV) determination of melamine
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15. Inhomogeneities of InGaN/GaN MOVPE multi quantum wells grown with two temperatures process studied by transmission electron microscopy.
16. Indium segregation in Al_1-xIn_xN investigated by photoluminescence under hydrostatic pressure
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19. Development of a histamine acoustic sensor using film of molecularly imprinted polymer prepared by electrochemical co-polymerisation of bis(bithiophene) derivatives
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21. Carrier recombination under one-photon and two-photon excitation in GaN epilayers
22. Blue laser diodes manufacturing in Poland
23. X-ray Diffraction as a Tool of InGaN layer Characterization.
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31. Rietveld refinement for polycrystalline indium nitride
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33. PLASTIC PROPERTIES OF GaN AND Al₂O₃ CRYSTAL: FEM-SIMULATION OF NANOINDENTATION CONFIRMED BY HIGH-RESOLUTION MICROSCOPY
34. Microstructure of homoepitaxially grown InGaN/GaN, violet light emitting laser diodes.
35. Modeling of elastic, piezoelectric and optical properties of vertically correlated GaN/AlN quantum dots
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37. Bowing of epitaxial structures grown on bulk GaN substrates
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