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

TL;DR

The study reports a giant isotope effect on the excited-state lifetime of the silicon T centre, with deuterium variants living over five times longer than protium, driven by suppression of nonradiative decay due to a lower C–H stretching vibration energy. By combining resonant lifetime measurements with first-principles calculations, it shows that excluding the standard accepting-mode multiphonon decay, the C–H stretch mode dominates nonradiative loss and accounts for the isotope dependence, predicting near-unit quantum efficiency for deuterium ($η_D \approx 98.4\%$). The work estimates radiative lifetime around $τ_R \approx 4.9 \, μs$ and increases the total zero-phonon radiative emission from ~4% to ~23% for the natural to deuterium variants, implying substantial improvements for single-photon sources and quantum memories in silicon. These results highlight isotopic engineering as a powerful lever to boost solid-state quantum emitters and spin–photon interfaces, with practical impact for quantum networking and silicon photonics.

Abstract

Efficient single-photon emitters are desirable for quantum technologies including quantum networks and photonic quantum computers. We investigate the T centre, 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 centre is over five times longer than the common protium variant. Through explicit first-principles calculations, we demonstrate that this dramatic difference is due to a reduction in the carbon-hydrogen local vibrational mode energy, which suppresses non-radiative decay. Our results imply that the deuterium T centre approaches unit quantum efficiency, enabling more efficient single-photon sources, quantum memories, and entanglement generation.

Figures (4)

• Figure 1: Photoluminescence spectra of T centre samples with varying isotopic composition. Each peak is labelled with the attributed structure, following a C_S,C_W,H labelling scheme. Sample A (orange) is the natural isotope distribution. Sample B (blue) is deuterated. Sample C (green) is grown with an elevated concentration of ^13C. (Inset) Atomic structure of the T centre showing the inequivalent carbon sites C_S (dangling bond) and C_W (bonded to hydrogen).
• Figure 2: Luminescence transient decay of T centre isotope variants under pulsed resonant excitation. The inset shows an enlarged view of the region enclosed by the dashed box.
• Figure 3: The nonradiative decay rate $\Gamma_{\rm NR}$ of the natural (red) and deuterium (blue) T centre evaluated for the accepting and C-H stretching modes. The dashed lines correspond to the experimental lifetimes of 0.884µs (red) and 4.807µs (blue), and the gray, shaded region highlights the range within one order of magnitude of the experimental values.
• Figure 4: Resonant photoluminescence spectrum of the natural T centre (Sample A), showing the region near the expected C–H stretch LVM energy. The black curve shows the background-subtracted and system-response–normalized data, while the red curve shows the background signal.