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Researchers in the EEEL Optoelectronics Division have demonstrated novel GaN nanowire MESFET devices. These structures are primarily being developed as test elements for use in extracting fundamental transport properties of nanowires. The GaN NW-MESFET devices developed by NIST are the best such devices reported in the world as far as we know. Comparatively, the NIST devices display the best Schottky diode ideality factor, lowest pinch-off voltage, lowest hysteresis, and highest drain-source on-off ratios.
Nanowire based electronics and optoelectronic structures are gaining importance for a variety of applications including super-efficient solid-state lighting and photovoltaics, RF NEMs, chemical and biological sensors, and various other needs. GaN is a particularly attractive material since it is chemically, thermally, and mechanically robust, and the nanowire morphology of GaN produces nearly perfect defect- and strain-free crystals that cannot be realized in conventional planar or bulk forms. Because of these compelling applications, there are growing demands for measurements of fundamental properties of individual nanowires and arrayed ensembles of nanowires.
Metrology of GaN nanowires is a challenging new science. One approach to extract fundamental electrical quantities such as carrier concentration, mobility, and Schottky barrier height involves the fabrication and testing of individual NW-MESFET structures. Extraction of such fundamental parameters is both experimentally and computationally challenging. EEEL is also working with collaborators at the University of Colorado to develop methods of conformal electrode deposition and collaborators at Georgia Tech-Savannah on the development of simulation tools for these devices. The GaN nanowires are grown by molecular beam epitaxy at the NIST Boulder Laboratories (as described in previous reports) and are among the highest quality nanowires reported in the world.
Work is proceeding to refine these results, adapt the devices to RF electronic and sensor applications, and further increase their utility for measuring fundamental transport properties of the GaN nanowires. The results are summarized in the forthcoming paper, “Metal-Semiconductor Field Effect Transistors (MESFETs) Made From Individual GaN Nanowires,” by Paul T. Blanchard et al., which is scheduled to appear in the IEEE Transactions on Nanotechnology.
For more information contact: Norman Sanford, phone 303-497-5239
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