Chemical-electronic coupling and the InAs two-dimensional electron gas
Dr. April S. Brown, John Cocke Professor of Electrical and Computer Engineering at Duke University, discusses how the origin of surface donors yielding the InAs surface-potential confined two-dimensional electron gas (2DEG) remains unknown, but is believed to be defect-based and therefore related to surface reconstruction, strain, and/or native defects associated with surface processes such as oxidation. We show that the surface oxide (either engineered or “native”) can be used as a reagent in surface-based chemical interactions modifying surface molecular attachment, both conformation and coverage, in a concentration-dependent fashion. These molecular interactions can be, in turn, “sensed” through changes in the 2DEG density and mobility.
More About the Lecture
Using x-ray photoelectron spectroscopy (XPS) and Hall measurements, we show that changes in the oxide chemistry resulting from surface DNA and protein interactions are sensitively reflected in changes in the 2DEG density and mobility. As an electronic sensor, biomolecule (DNA/protein) adsorption can be measured down to fM concentrations with dynamic range of greater than four orders of magnitude. DNA hybridization can also be electronically sensed and differentiated from non-specific binding in the fM concentration range. These results, realized with a planar device implementation, show performance equal to that realized in a nanowire-based device.
At higher concentrations (μM), adsorbed single-stranded DNA (ssDNA) average conformation and coverage is highly dependent on the evolving oxide chemistry that changes from In-oxide (In2O3)- to As-oxide (As2O3/As2O5)-rich or lean as a result of specific DNA ligand interactions. These changes are readily “read-out” in 2DEG density and mobility changes. We find that amine groups bind to the As/As oxide and that As oxide-richness can lead to the creation of dense ssDNA brushes associated with changes in the hydrogen bonding network as determined with FTIR.
About the Speaker
Dr. April S. Brown is the John Cocke Professor of Electrical and Computer Engineering at Duke University. She received her Ph.D. degree from Cornell University in 1985. She worked at the Hughes Research Laboratories (now HRL LLC) in Malibu, Ca. from 1986-1993, and spent one year at the Army Research Office in the Physics Division (1988). She was at the Georgia Institute of Technology (1994-2002) as the Pettit Professor in Microelectronics where she also served as Associate Dean in the College of Engineering and as Executive Assistant to the President. She joined Duke University as Professor and Chair in July 2002. She is currently Sr. Associate Dean for Research in the Pratt School of Engineering. Professor Brown’s research has focused on epitaxial growth of InP - and GaN-based semiconductors, material characterization and microelectronic devices.
Professor Brown is Fellow of IEEE and the American Physical Society. She received the Paul Rappaport Award from the IEEE Electron Device Society and has also been a Distinguished Lecturer of this Society. She received the Georgia Tech Women’s Leadership Award in 2001.
Sponsored Lecture: Part of the ECE Distinguished Lecture series by the Electrical and Computer Engineering department. Webcast sponsored by MconneX. Contact Sandra Hines at MconneXion@umich.edu with questions about webcasting.