Abstract
In oxygenic plants, photons are captured with high
quantum efficiency by two specialized reaction centers (RC) called
Photosystem I (PS I) and Photosystem II (PS II). The captured
photon triggers rapid charge separation and the photon energy is
converted into an electrostatic potential across the nanometer-scale
nm reaction centers. The exogenous photovoltages from a
single PS I RC have been previously measured using the technique
of Kelvin force probe microscopy (KFM). However, biomolecular
photovoltaic applications require two-terminal devices. This
paper presents for the first time, a micro-device for detection
and characterization of isolated PS I RCs. The device is based
on an AlGaN/GaN high electron mobility transistor (HEMT)
structure. AlGaN/GaN HEMTs show high current throughputs
and greater sensitivity to surface charges compared to other
field-effect devices. PS I complexes immobilized on the floating
gate of AlGaN/GaN HEMTs resulted in significant changes in the
device characteristics under illumination. An analytical model has
been developed to estimate the RCs of a major orientation on the
functionalized gate surface of the HEMTs.
