Functionalized Semiconductor nanostructures and devices
Group III-nitride electrolyte gate field effect transistors (EGFETs) have recently been demonstrated to exhibit excellent properties for biochemical sensor applications, such as pH-sensitive field effect transistors or electrical monitoring of action potentials generated by living cells. High Electron Mobility Transistors (HEMTs) make use of the two-dimensional electron gas which spontaneously forms at the interface between a GaN substrate and a few nm thick AlGaN surface layer. Besides their chemical inertness and the high pH-sensitivity of group III-nitride surfaces, the high signal-to-noise ration of GaN based HEMT structures is a major advantage compared to conventional devices such as silicon MOS structures.
The covalent attachment of tailored monomolecular films with molecular level control over structural order and composition on group III-nitride device surfaces allows the realization of bioelectronic interfaces for the investigation of semiconductor-molecule charge transfer or for applications in sensors based on molecular recognition. One example is the specific antibody detection or label-free detection of DNA hybridization. To this end we investigate the formation of self assembled monolayers (SAMs) of aminopropyltriethoxysilane (APTES) on GaN and AlN surfaces. The reactive amino group of APTES molecules can be used as an anchor for the immobilization of single stranded DNA molecules via Schiff-base formation. AlGaN/GaN EGFETs with such a surface functionalization will be used to electronically detect hybridization with complementary DNA molecules. This work is supported by DFG (SFB 563).
