Red Luminescence from a Chlorine Zinc Vacancy Complex in ZnSe: In the search for interesting defects for quantum applications, we identified the Chlorine Zinc-Vacancy Complex as a prevalent defect in n-type Cl-doped ZnSe. The image illustrates the defect with its highest occupied electron orbitals. The red luminescence corresponds to the emission wavelength of this complex in its -1 charge state, the dominant charge state for this defect in n-type ZnSe. We are grateful for the support and advice from Program Manager Dr. Ali Sayir and acknowledge the AFOSR Grant No. FA9550-21-1-0383. Contributors: Kelsey J. Mirrielees, Yifeng Wu, Douglas L. Irving