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Imaging the p-n junction in a gallium nitride nanowire with a scanning microwave microscope

Published

Author(s)

Atif A. Imtiaz, Thomas M. Wallis, Joel C. Weber, Kevin J. Coakley, Matthew D. Brubaker, Paul T. Blanchard, Kristine A. Bertness, Norman A. Sanford

Abstract

We used a broadband, atomic-force-microscope-based, scanning microwave microscope (AFM-SMM) to probe the axial dependence of the depletion in a GaN nanowire (NW) p-n junction structure. The NWs were c-axis oriented and grown by molecular beam epitaxy. The estimated respective doping concentrations in the n- and p-type regions were (0.2—0.9)×1017 cm-3 (Si) and ≈1×1018 cm-3 (Mg). The AFM-SMM operated in the range of 1—20 GHz. The quantity d((S_11))⁄dV, which is the derivative with respect to voltage of RF reflection coefficient S_11, varied strongly when probing axially along the NW and across the p-n junction. The axial variation in d((S_11))⁄dV essentially mapped the asymmetric depletion arising from the doping concentrations on either side of the junction. The results reveal that AFM-SMM is a useful method with which to spatially map electrical properties of a semiconductor nanostructure without the need to make separate electrical contact to the device.  
Citation
Applied Physics Letters
Volume
104
Issue
26
Created July 2, 2014, Updated January 27, 2020