The nuclear spins of low-density implanted Ga atoms in Ge are interesting candidates for solid state-based qubits. To date, activation studies of implanted Ga in Ge have focused on high densities. Here we extend activation studies into the low-density regime. We use spreading resistance profiling and secondary ion mass spectrometry to derive electrical activation of Ga ions implanted into Ge as a function of rapid thermal anneal temperature and implant density. We show that for our implant conditions the activation is best for anneal temperatures between 400 and 650 ∘C, with a maximum activation of 64% at the highest fluence. Below 400 ∘C, remaining implant damage results in defects that act as superfluous carriers, and above 650 ∘C, surface roughening and loss of Ga ions are observed. The activation increased monotonically from 10% to 64% as the implant fluence increased from 6×1010 to 6×1012 cm−2. The results provide thermal anneal conditions to be used for initial studies of using low-density Ga atoms in Ge as nuclear spin qubits.
@article{arxiv.2204.02878,
title = {Thermal activation of low-density Ga implanted in Ge},
author = {Natalie D. Foster and Andrew J. Miller and Troy A. Hutchins-Delgado and Christopher M. Smyth and Michael C. Wanke and Tzu-Ming Lu and Dwight R. Luhman},
journal= {arXiv preprint arXiv:2204.02878},
year = {2022}
}