Giant Isotope Effect on the Excited-State Lifetime and Emission Efficiency of the Silicon T Center

Efficient single-photon emitters are desirable for quantum technologies including quantum networks and photonic quantum computers. We investigate the T center, a telecommunications-band emitter in silicon, and find a strong isotope dependence of its excited-state lifetime. In particular, the lifetime of the deuterium T center is over five times longer than the common protium variant. We measure an isotope-dependent shift of the local vibrational carbon-hydrogen stretch mode energy and show through explicit first-principles calculations that the dramatic lifetime difference is consistent with strong suppression of nonradiative decay due to the reduced energy of this mode for deuterium T centers. Our results imply that the deuterium T center approaches unit quantum efficiency, enabling more efficient single-photon sources and quantum memories and improved readout of the T center electron spin.