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arXiv · 1910.06938

Three-dimensional imaging of beam-induced biasing of InP/GaInP tunnel diodes

Cristina Cordoba·Xulu Zeng·Daniel Wolf·Axel Lubk·Enrique Barrigón·Magnus T. Borgström·Karen L. Kavanagh
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Abstract

Electron Holographic Tomography was used to obtain 3-dimensional reconstructions of the morphology and electrostatic potential gradient of axial GaInP/InP nanowire tunnel diodes. Crystal growth was carried out in two opposite directions: GaInP:Zn/InP:S and InP:Sn/GaInP:Zn, using Zn as the p-type dopant in the GaInP, but with changes to the n-type dopant (S or Sn) in the InP. Secondary electron and electron beam induced current images obtained using scanning electron microscopy indicated the presence of p-n junctions in both cases and current-voltage characteristics measured via lithographic contacts showed the negative differential resistance, characteristic of band-to-band tunneling, for both diodes. EHT measurements confirmed a short depletion width in both cases ($21 \pm 3$ nm), but different built-in potentials, $V_{bi}$, of 1.0 V for the p-type (Zn) to n-type (S) transition, and 0.4 V for both were lower than the expected 1.5 V for these junctions, if degenerately-doped. Charging induced by the electron beam was evident in phase images which showed non-linearity in the surrounding vacuum, most severe in the case of the nanowire grounded at the \emph{p}-type Au contact. We attribute their lower $V_{bi}$ to asymmetric secondary electron emission, beam-induced current biasing and poor grounding contacts.

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Cristina Cordoba, Xulu Zeng, Daniel Wolf, Axel Lubk, Enrique Barrigón, Magnus T. Borgström, Karen L. Kavanagh. 2019-10-15. Three-dimensional imaging of beam-induced biasing of InP/GaInP tunnel diodes. https://doi.org/10.1021/acs.nanolett.9b00249

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