High-density structures of sub-surface phosphorus dopants in silicon continue to garner interest as a silicon-based quantum computer platform, however, a much-needed confirmation of their dopant arrangement has been lacking. In this work, we take advantage of the chemical specificity of X-ray photoelectron diffraction to obtain the precise structural configuration of P dopants in sub-surface Si:P δ-layers. The growth of δ-layer systems with different levels of doping is carefully studied and verified using X-ray photoelectron spectroscopy and low-energy electron diffraction. Subsequent XPD measurements reveal that in all cases, the dopants primarily substitute with Si atoms from the host material. Furthermore, no signs of free carrier-inhibiting P−P dimerization can be observed. Our observations not only settle a nearly decade-long debate about the dopant arrangement but also demonstrate that XPD is well suited to study sub-surface dopant structures. This work thus provides valuable input for an updated understanding of the behavior of Si:P δ-layers and the modeling of their derived quantum devices.
@article{arxiv.2211.10096,
title = {Probing the Atomic Arrangement of Sub-Surface Dopants in a Silicon Quantum Device Platform},
author = {Håkon I. Røst and Ezequiel Tosi and Frode S. Strand and Anna Cecilie Åsland and Paolo Lacovig and Silvano Lizzit and Justin W. Wells},
journal= {arXiv preprint arXiv:2211.10096},
year = {2023}
}