Monolayer doping of germanium with arsenic: A new chemical route to achieve optimal dopant activation
Kennedy, Noel; Garvey, Shane; Maccioni, Barbara; Eaton, Luke; Nolan, Michael; Duffy, Ray; Meaney, Fintan; Kennedy, Mary; Holmes, Justin D.; Long, Brenda
Date:
2020-08-03
Copyright:
© 2020 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in Langmuir, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://pubs.acs.org/doi/10.1021/acs.langmuir.0c00408
Full text restriction information:
Access to this article is restricted until 12 months after publication by request of the publisher.
Restriction lift date:
2021-08-03
Citation:
Kennedy, N., Garvey, S., Maccioni, B., Eaton, L., Nolan, M., Duffy, R., Meaney, F., Kennedy, M., Holmes, J. D. and Long, B. (2020) 'Monolayer Doping of Germanium with Arsenic: A New Chemical Route to Achieve Optimal Dopant Activation', Langmuir, 36(34), pp. 9993-10002. doi: 10.1021/acs.langmuir.0c00408
Abstract:
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.
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