Probing quantum defect states in Zr-doped homoepitaxial AlN

The neutral defect complex comprising zirconium substituting onto the Al sublattice (ZrAl) and an adjacent nitrogen vacancy (VN), (ZrAl−VN)0, in aluminum nitride (AlN) crystals is theoretically predicted to host unique spin states suitable for quantum manipulation. Here, we report experimental observations of both intradefect and band-to-impurity optical transitions involving (ZrAl− VN)0 in AlN. This defect was realized via in situ doping of Zr into AlN homoepitaxial layers grown by metalorganic chemical vapor deposition. Below-bandgap excitation at λexc = 260 nm resolved emission peaks at 1.89, 2.11, and 3.52 eV, in excellent agreement with those predicted by first-principles calculations for the intradefect and band-to-impurity type of transitions involving (ZrAl− VN)0, providing experimental validation of the defect's electronic structure. Temperature-dependent PL further demonstrates that the (ZrAl− VN)0 state maintains a stable optical emission up to room temperature, with a high thermal activation energy of 48 meV, indicative of thermal robustness against nonradiative quenching. While further spin-based measurements are needed to assess coherence and manipulation limits, experimental and theoretical findings validate Zr-doped AlN as a promising platform for the realization of room-temperature quantum defect devices, including solid-state qubits and integrated quantum photonic technologies.