Thermal activation of low-density Ga implanted in Ge

Abstract

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 ${}^{\circ }$C, with a maximum activation of 64% at the highest fluence. Below 400 ${}^{\circ }$C, remaining implant damage results in defects that act as superfluous carriers, and above 650 ${}^{\circ }$C, surface roughening and loss of Ga ions are observed. The activation increased monotonically from 10% to 64% as the implant fluence increased from $6\times 10^{10}$ to $6\times 10^{12}$ 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.

arXiv comment7 pages, 4 figures

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