Dresden 2009 – scientific programme

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BP: Fachverband Biologische Physik

BP 11: Novel Methods

BP 11.8: Talk

Tuesday, March 24, 2009, 16:15–16:30, ZEU 260

Impedance study of AlGaN/GaN HEMT structures in contact with electrolyte solutions — Michael Charpentier, •Hartmut Witte, Christian Warnke, Mathias Müller, Kay-Michael Günther, Armin Dadgar, and Alois Krost — Otto-von-Guericke-University-Magdeburg, Institute of Experimental Physics, 39016 Magdeburg

Planar multi-electrode-arrays (MEA) are widely spread for stimulation and recording of neuron network signals. Besides metal electrodes and Silicon, more and more group-III-nitride devices are used as substrates. For MEA applications the substrate impedance as one of the main signal transfer parameters has to be optimized. In this contribution we investigate the total impedance of AlGaN/GaN high electron mobility structures (HEMT) using impedance spectroscopy between 20 Hz and 2 MHz. The total impedance is composed of the contributions of the two dimensional electron gas (2DEG), the metal contacts and the horizontal and vertical layer material impedances. The impacts of these parts were studied by varying the layer arrangement and applied bias voltages, by using a MESA microstructuring, and by illumination of the samples. All variations significantly change the impedance spectra. Furthermore, samples with different total impedances show disparate signal behavior in contact with electrolyte solutions with varying pH-values and conductivities. Therefore, these investigations are useful for optimization of the device performance for different biosensor applications.