Identification of the I$_{10}$ Donor in ZnO as a Sn--Li Complex with Large Hyperfine Interaction

TL;DR

This study identifies a Sn--Li complex as the I$_{10}$ donor in ZnO, demonstrating its large hyperfine interaction and potential for quantum spin-photon applications through combined experimental and theoretical analysis.

Contribution

The paper uncovers the microscopic origin of the I$_{10}$ donor in ZnO as a Sn--Li complex, revealing its large hyperfine interaction and implications for quantum technologies.

Findings

Sn--Li complex confirmed as I$_{10}$ donor in ZnO

Hyperfine interaction measured at 392 MHz

Enhanced thermal robustness and nuclear spin control potential

Abstract

Donor impurities in wide direct band gap semiconductors provide a promising platform for spin--photon quantum technologies by combining a donor spin qubit with optically addressable transitions. In ZnO, the shallow donor with the largest reported binding energy has long been associated with the I$_{10}$ bound exciton line, but its microscopic origin has remained unresolved. Here we demonstrate the controlled formation and identification of this donor as a Sn--Li complex through a combination of ion implantation, annealing, optical spectroscopy, and first-principles calculations. Resonant two-laser coherent population trapping measurements reveal an electron--$^{119}$Sn hyperfine interaction of $392 \pm 15$\,MHz, establishing a coupled electron--spin--1/2, nuclear--spin--1/2 system with one of the largest hyperfine couplings reported for shallow donors in semiconductors. Density functional theory calculations show that a nearest-neighbor Sn$_{\mathrm{Zn}}$--Li$_{\mathrm{Zn}}$ complex has favorable formation energetics, donor character with the electron localized on Sn, and an extrapolated hyperfine interaction consistent with experiment. The large donor binding energy and excited-state structure indicate enhanced thermal robustness of the optical transition relative to conventional group--III donors, while the strong hyperfine interaction enables fast electron--nuclear spin control and prospects for direct nuclear--spin--photon interfaces. We further observe efficient optically induced nuclear spin polarization, highlighting a path toward nuclear spin initialization. More broadly, our results reveal how a donor--acceptor complex can access previously unexplored regimes of shallow donor physics, extending the design space of quantum defects beyond isolated substitutional dopants.