Monolayer Doping of Germanium with Arsenic: A New Chemical Route to Achieve Optimal Dopant Activation

Noel Kennedy, Shane Garvey, Barbara Maccioni, Luke Eaton, Michael Nolan, Ray Duffy, Fintan Meaney, Mary Kennedy, Justin D. Holmes, Brenda Long

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


Reported here is a new chemical route for the wet chemical functionalization of germanium (Ge), whereby arsanilic acid is covalently bound to a chlorine (Cl)-terminated surface. This new route is used to deliver high concentrations of arsenic (As) dopants to Ge, via monolayer doping (MLD). Doping, or the introduction of Group III or Group V impurity atoms into the crystal lattice of Group IV semiconductors, is essential to allow control over the electronic properties of the material to enable transistor devices to be switched on and off. MLD is a diffusion-based method for the introduction of these impurity atoms via surface-bound molecules, which offers a nondestructive alternative to ion implantation, the current industry doping standard, making it suitable for sub-10 nm structures. Ge, given its higher carrier mobilities, is a leading candidate to replace Si as the channel material in future devices. Combining the new chemical route with the existing MLD process yields active carrier concentrations of dopants (>1 × 1019 atoms/cm3) that rival those of ion implantation. It is shown that the dose of dopant delivered to Ge is also controllable by changing the size of the precursor molecule. X-ray photoelectron spectroscopy (XPS) data and density functional theory (DFT) calculations support the formation of a covalent bond between the arsanilic acid and the Cl-terminated Ge surface. Atomic force microscopy (AFM) indicates that the integrity of the surface is maintained throughout the chemical procedure, and electrochemical capacitance voltage (ECV) data shows a carrier concentration of 1.9 × 1019 atoms/cm3 corroborated by sheet resistance measurements.

Original languageEnglish
Pages (from-to)9993-10002
Number of pages10
JournalLangmuir : the ACS journal of surfaces and colloids
Issue number34
Early online date3 Aug 2020
Publication statusPublished (in print/issue) - 1 Sept 2020

Bibliographical note

Publisher Copyright:
Copyright © 2020 American Chemical Society.

Copyright 2020 Elsevier B.V., All rights reserved.


  • Monolayer doping
  • arsenic
  • germanium
  • functionalisation
  • click chemistry
  • carrier concentration


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